Construct validity of the dependence syndrome as measured by DSM-IV for different psychoactive substances

Comparing factor, class, and mixture models of cannabis initiation and DSM cannabis use disorder criteria, including craving, in the Brisbane longitudinal twin study

Accumulating evidence suggests that the Diagnostic and Statistical Manual of Mental Disorders (DSM) diagnostic criteria for cannabis abuse and dependence are best represented by a single underlying factor. However, it remains possible that models with additional factors, or latent class models or hybrid models, may better explain the data. Using structured interviews, 626 adult male and female twins provided complete data on symptoms of cannabis abuse and dependence, plus a craving criterion. We compared latent factor analysis, latent class analysis, and factor mixture modeling using normal theory marginal maximum likelihood for ordinal data. Our aim was to derive a parsimonious, best-fitting cannabis use disorder (CUD) phenotype based on DSM-IV criteria and determine whether DSM-5 craving loads onto a general factor. When compared with latent class and mixture models, factor models provided a better fit to the data. When conditioned on initiation and cannabis use, the association between criteria for abuse, dependence, withdrawal, and craving were best explained by two correlated latent factors for males and females: a general risk factor to CUD and a factor capturing the symptoms of social and occupational impairment as a consequence of frequent use. Secondary analyses revealed a modest increase in the prevalence of DSM-5 CUD compared with DSM-IV cannabis abuse or dependence. It is concluded that, in addition to a general factor with loadings on cannabis use and symptoms of abuse, dependence, withdrawal, and craving, a second clinically relevant factor defined by features of social and occupational impairment was also found for frequent cannabis use.

A randomized, double-blind evaluation of buprenorphine taper duration in primary prescription opioid abusers

IMPORTANCE

Although abuse of prescription opioids (POs) is a significant public health problem, few experimental studies have investigated the treatment needs of this growing population.

OBJECTIVE

To evaluate, following brief stabilization with a combination of buprenorphine hydrochloride and naloxone hydrochloride dihydrate, the relative efficacy of 1-, 2-, and 4-week buprenorphine tapering regimens and subsequent naltrexone hydrochloride therapy in PO-dependent outpatients.

DESIGN, SETTING, AND PARTICIPANTS

A double-blind, 12-week randomized clinical trial was conducted in an outpatient research clinic. Following a brief period of buprenorphine stabilization, 70 PO-dependent adults were randomized to receive 1-, 2-, or 4-week tapers followed by naltrexone therapy.

INTERVENTION

During phase 1 (weeks 1-5 after randomization), participants visited the clinic daily; during phase 2 (weeks 6-12), visits were reduced to thrice weekly. Participants received behavioral therapy and urine toxicology testing throughout the trial.

MAIN OUTCOMES AND MEASURES

The percentage of participants negative for illicit opioid use, retention, naltrexone ingestion, and favorable treatment response (ie, retained in treatment, opioid abstinent, and receiving naltrexone at the end of the study).

RESULTS

Opioid abstinence at the end of phase 1 was greater in the 4-week compared with the 2- and 1-week taper conditions (P = .02), with 63% (n = 14), 29% (n = 7), and 29% (n = 7) of participants abstinent in the 4-, 2-, and 1-week conditions, respectively. Abstinence at the end of phase 2 was also greater in the 4-week compared with the 2- and 1-week conditions (P = .03), with 50% (n = 11), 16% (n = 4), and 20% (n = 5) of participants abstinent in the 4-, 2-, and 1-week conditions, respectively. There were more treatment responders in the 4-week condition (P = .03), with 50% (n = 11), 17% (n = 4), and 21% (n = 5) of participants in the 4-, 2-, and 1-week groups considered responders at the end of treatment, respectively. Retention and naltrexone ingestion also were superior in the 4-week vs briefer tapers (both P = .04). Experimental condition (ie, taper duration) was the strongest predictor of treatment response, followed by buprenorphine stabilization dose.

CONCLUSIONS AND RELEVANCE

This study represents a rigorous experimental evaluation of outpatient buprenorphine stabilization, brief taper, and naltrexone maintenance for treatment of PO dependence. Results suggest that a meaningful subset of PO-dependent outpatients may respond positively to a 4-week taper plus naltrexone maintenance intervention.

Evaluating brief screeners to discriminate between drug use disorders in a sample of treatment-seeking adults

OBJECTIVE

The objective was to identify a potential core set of brief screeners for the detection of individuals with a substance use disorder (SUD) in medical settings.

METHOD

Data were from two multisite studies that evaluated stimulant use outcomes of an abstinence-based contingency management intervention as an addition to usual care (National Drug Abuse Treatment Clinical Trials Network trials 006-007). The sample comprised 847 substance-using adults who were recruited from 12 outpatient substance abuse treatment settings across the United States. Alcohol and drug use disorders were assessed by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Checklist. Data were analyzed by factor analysis, item response theory (IRT), sensitivity and specificity procedures.

RESULTS

Comparatively prevalent symptoms of dependence, especially inability to cut down for all substances, showed high sensitivity for detecting an SUD (low rate of false negative). IRT-defined severe (infrequent) and low discriminative items, especially withdrawal for alcohol, cannabis and cocaine, had low sensitivity in identifying cases of an SUD. IRT-defined less severe (frequent) and high discriminative items, including inability to cut down or taking larger amounts than intended for all substances and withdrawal for amphetamines and opioids, showed good-to-high values of area under the receiver operating characteristic curve in classifying cases and noncases of an SUD.

CONCLUSION

Findings suggest the feasibility of identifying psychometrically reliable substance dependence symptoms to develop a two-item screen for alcohol and drug disorders.

Relationship of substance abuse to dependence in the U.S. general population

OBJECTIVE

The diagnostic categories of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, for substance abuse and dependence are commonly used in clinical work and research studies, but whether abuse and dependence represent two different syndromes has been debated. The purpose of this article is to investigate the relationship of substance abuse and dependence for cannabis, cocaine, stimulants and sedatives among lifetime users of these substances in the National Epidemiologic Survey on Alcohol and Related Conditions, a nationally representative survey conducted in 2001-2002.

METHOD

The multiple indicators multiple causes (MIMIC) model addresses three sets of relationships: those between (1) diagnostic criteria and latent factors, (2) latent factors and covariates, and (3) criteria and covariates. This approach allows for the detection of and compensation for noninvariance of the measurement of criteria across subgroups.

RESULTS

Compared with one-factor models, two-factor models (factors roughly corresponding to abuse and dependence) fit significantly better across all substances, with abuse and dependence factors highly correlated. The MIMIC model indicated that race/ethnicity, age, income, and marital status showed some differential relationships across substance groups, although most covariates showed similar associations to dependence and abuse factors. Noninvariance of criteria measurement by demographic covariates was most pronounced for cannabis abuse and dependence criteria.

CONCLUSIONS

The general relationship of abuse to dependence was consistent across substances. Results were equivocal on the value of retaining separate factors; therefore, investigating the relationships of specific genetic variants and treatment outcomes to dimensional indicators of abuse, dependence, and measures combining these criteria is warranted. Measurement of cannabis abuse and dependence criteria appears most affected by demographic characteristics.

Analyses related to the development of DSM-5 criteria for substance use related disorders: 2. Proposed DSM-5 criteria for alcohol, cannabis, cocaine and heroin disorders in 663 substance abuse patients

BACKGROUND

A number of changes have been proposed and investigated in the criteria for substance use disorders in DSM-5. However, although clinical utility of DSM-5 is a high priority, relatively little of the empirical evidence supporting the changes was obtained from samples of substance abuse patients.

METHODS

Proposed changes were examined in 663 patients in treatment for substance use disorders, evaluated by experienced clinicians using the Psychiatric Research Interview for Substance and Mental Disorders (PRISM). Factor and item response theory analysis was used to investigate the dimensionality and psychometric properties of alcohol, cannabis, cocaine and heroin abuse and dependence criteria, and craving.

RESULTS

The seven dependence criteria, three of the abuse criteria (hazardous use; social/interpersonal problems related to use; neglect of roles to use), and craving form a unidimensional latent trait for alcohol, cannabis, cocaine and heroin. Craving did not add significantly to the total information offered by the dependence criteria, but adding the three abuse criteria and craving together did significantly increase total information for the criteria sets associated with alcohol, cannabis and heroin.

CONCLUSION

Among adult patients in treatment for substance disorders, the alcohol, cannabis, cocaine and heroin criteria for dependence, abuse (with the exception of legal problems), and craving measure a single underlying dimension. Results support the proposal to combine abuse and dependence into a single diagnosis in the DSM-5, omitting legal problems. Mixed support was provided for the addition of craving as a new criterion, warranting future studies of this important construct in substance use disorders.

Are the symptoms of cannabis use disorder best accounted for by dimensional, categorical, or factor mixture models? A comparison of male and female young adults

Despite the consensus that criteria for cannabis abuse and dependence and symptoms of withdrawal are best explained by a single latent liability, it remains unknown whether alternative models provide a better explanation of these criteria. A series of latent factor, latent class, and hybrid factor mixture models were fitted to data from 872 recent cannabis users from the Minnesota Twin Family Study who completed Diagnostic and Statistical Manual of Mental Disorders (3rd ed., revised, and 4th ed.) diagnostic criteria for cannabis abuse, dependence, and symptoms of withdrawal. Despite theoretical appeal, results did not support latent class or factor mixture modeling. Instead, symptoms of abuse, dependence, and withdrawal were better summarized by a single latent factor Cannabis Use Disorder (CUD) for male and female young adults. An almost 2-fold sex difference in item endorsement was best explained by a single mean difference on the CUD factor, indicating that young men have a greater latent liability toward expressing CUD.

A survey study to characterize use of Spice products (synthetic cannabinoids)

BACKGROUND

Synthetic cannabinoids are a rapidly emerging class of abused drugs. Synthetic cannabinoids are typically sold as "herbal blends" or "incense," commonly referred to as Spice products. No controlled human experiments have been conducted on the effects of Spice products or the synthetic cannabinoids they often contain.

METHODS

An internet-based survey study was conducted with adults reporting at least one lifetime use of a Spice product.

RESULTS

Respondents were primarily male, Caucasian and ≥ 12 years of education. Use of other psychoactive drugs was common, though 21% identified Spice products as their preferred drug. Spice products were most frequently obtained from retail vendors and smoked, though other forms of ingestion were endorsed. Mean age of first use was 26 and mean frequency of use in the past year was 67 days (range 0-365). Primary reasons for use were curiosity, positive drug effect, relaxation, and to get high without having a positive drug test. Acute subjective effects were similar to known effects of cannabis, and a subset of users met DSM criteria for abuse and dependence on Spice products.

CONCLUSIONS

Participants exhibited a diverse profile of use patterns as is typical for other drugs of abuse. There was evidence that users continued to seek and use these drugs after being banned by local authorities. This study should be interpreted with caution due to methodological limitations. Controlled laboratory research is needed to further examine the behavioral pharmacology of individual synthetic cannabinoids found in Spice products.

Psychometric modeling of cannabis initiation and use and the symptoms of cannabis abuse, dependence and withdrawal in a sample of male and female twins

BACKGROUND

Despite an emerging consensus that the DSM-IV diagnostic criteria for cannabis abuse and dependence are best represented by a single underlying liability, it remains unknown if latent class or hybrid models can better explain the data.

METHOD

Using structured interviews, 7316 adult male and female twins provided complete data on DSM-IV symptoms of cannabis abuse and dependence. Our aim was to derive a parsimonious, best-fitting cannabis use disorder (CUD) phenotype based on DSM-III-R/IV criteria by comparing an array of psychometric models (latent factor analysis, latent class analysis and factor mixture modeling) using full information maximum likelihood ordinal data methods in Mx.

RESULTS

We found little evidence to support population heterogeneity since neither latent class nor hybrid factor mixture models provided a consistently good fit to the data. When conditioned on initiation and cannabis use, the endorsement patterns of the abuse, dependence and withdrawal criteria were best explained by two latent factors for males and females. The first was a general CUD factor for which genetic effects explained 53-54% of the variance. A less interpretable second factor included a mix of cross-loading dependence and withdrawal symptoms.

CONCLUSIONS

This is the first study to compare competing measurement models to derive an empirically determined CUD phenotype. Commensurate with proposed changes to substance use disorders in the DSM-V, our results support an emerging consensus that a single CUD latent factor can more optimally assess the risk or liability underpinning correlated measures of use, abuse, dependence and withdrawal criterion.

DSM-IV alcohol abuse due to hazardous use: a less severe form of abuse?

OBJECTIVE

A majority of individuals that meet criteria for alcohol abuse based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), do so by endorsing the hazardous use criterion. We used a large, nationally representative data set to investigate whether alcohol abuse due to hazardous use is distinct from abuse attributable to other abuse criteria and whether abuse due to hazardous use is a less severe form of alcohol abuse.

METHOD

Two waves of data, collected 3 years apart, from 34,653 individuals who participated in the National Epidemiological Survey on Alcohol and Related Conditions were used. Logistic regression was used to compare those with alcohol abuse due to hazardous use and those with alcohol abuse due to other criteria across several sociodemographic and psychiatric correlates at Wave 1 and across alcohol-related outcomes at the 3-year follow-up. Those with a lifetime history of alcohol dependence at Wave 1 were excluded.

RESULTS

Abuse due to hazardous use was more commonly noted in older individuals, those not living below the poverty line, and those without nicotine dependence and was more likely to be noted in White participants. Abuse due to hazardous use was also associated with lower rates of problematic drinking, alcohol dependence, and help seeking at 3-year follow-up.

CONCLUSIONS

Individuals endorsing hazardous use are at greater risk than those endorsing no abuse criteria, but abuse due to hazardous use may represent a less severe form of alcohol-use disorders. This is troubling, because current DSM conceptualizations allow for endorsement of hazardous use to denote alcohol-use disorders. Future classifications may wish to consider a higher threshold for alcohol-use disorders, particularly when hazardous use is endorsed.

Abuse and dependence on prescription opioids in adults: a mixture categorical and dimensional approach to diagnostic classification

BACKGROUND

For the emerging DSM-V, it has been recommended that dimensional and categorical methods be used simultaneously in diagnostic classification; however, little is known about this combined approach for abuse and dependence.

METHOD

Using data (n=37 708) from the 2007 National Survey on Drug Use and Health (NSDUH), DSM-IV criteria for prescription opioid abuse and dependence among non-prescribed opioid users (n=3037) were examined using factor analysis (FA), latent class analysis (LCA, categorical), item response theory (IRT, dimensional), and factor mixture (hybrid) approaches.

RESULTS

A two-class factor mixture model (FMM) combining features of categorical latent classes and dimensional IRT estimates empirically fitted more parsimoniously to abuse and dependence criteria data than models from FA, LCA and IRT procedures respectively. This mixture model included a severely affected group (7%) with a comparatively moderate to high probability (0.32-0.88) of endorsing all abuse and dependence criteria items, and a less severely affected group (93%) with a low probability (0.003-0.16) of endorsing all criteria. The two empirically defined groups differed significantly in the pattern of non-prescribed opioid use, co-morbid major depression, and substance abuse treatment use.

CONCLUSIONS

A factor mixture model integrating categorical and dimensional features of classification fits better to DSM-IV criteria for prescription opioid abuse and dependence in adults than a categorical or dimensional approach. Research is needed to examine the utility of this mixture classification for substance use disorders and treatment response.

Cannabis dimensionality: dependence, abuse and consumption

AIMS

Genetic research on substance use disorders usually defines phenotypes as a binary diagnosis, resulting in a loss of information if the disorder is inherently dimensional. The DSM-IV criteria for drug dependence were based on a theoretically dimensional (linear) model. Considerable investigation has been conducted on DSM-IV alcohol criteria, but less is known about the dimensionality of DSM-IV cannabis criteria for abuse and dependence. The aim of this study is to assess whether DSM-IV cannabis dependence (including withdrawal) and abuse criteria fit a linear measure of severity and whether a consumption criterion adds linearly to severity.

DESIGN/SETTING/PARTICIPANTS/MEASUREMENTS

Participants were 8172 in the National Epidemiologic Survey on Alcohol and Related Conditions who had ever used cannabis. Wald statistics were used to test whether categorical, dimensional or hybrid forms best fit the data. We examined the following as criterion sets: (1) dependence; (2) dependence and abuse; and (3) dependence, abuse and frequency of use. Validating variables included family history of drug problems, early onset of cannabis use, and antisocial personality disorder.

FINDINGS

For cannabis dependence, no evidence was found for categorical or hybrid models; Wald tests indicated that models representing the seven DSM-IV dependence criteria as a linear severity measure best described the association between the criteria and validating variables. However, significant differences from linearity occurred after adding the four cannabis abuse criteria (p=0.03) and the use indicator (p=0.01) for family history and antisocial personality disorder.

CONCLUSION

With ample power to detect non-linearity, cannabis dependence was shown to form an underlying continuum of severity. However, adding abuse criteria, with and without a measure of consumption, resulted in a model that differed significantly from linearity for two of the three validating variables.

Using a latent variable approach to inform gender and racial/ethnic differences in cocaine dependence: a National Drug Abuse Treatment Clinical Trials Network study

This study applies a latent variable approach to examine gender and racial/ethnic differences in cocaine dependence, to determine the presence of differential item functioning (DIF) or item-response bias to diagnostic questions of cocaine dependence, and to explore the effects of DIF on the predictor analysis of cocaine dependence. The analysis sample included 682 cocaine users enrolled in two national multisite studies of the National Drug Abuse Treatment Clinical Trials Network (CTN). Participants were recruited from 14 community-based substance abuse treatment programs associated with the CTN, including 6 methadone and 8 outpatient nonmethadone programs. Factor and multiple indicators-multiple causes (MIMIC) procedures evaluated the latent continuum of cocaine dependence and its correlates. MIMIC analysis showed that men exhibited lower odds of cocaine dependence than women (regression coefficient, beta = -0.34), controlling for the effects of DIF, years of cocaine use, addiction treatment history, comorbid drug dependence diagnoses, and treatment setting. There were no racial/ethnic differences in cocaine dependence; however, DIF by race/ethnicity was noted. Within the context of multiple community-based addiction treatment settings, women were more likely than men to exhibit cocaine dependence. Addiction treatment research needs to further evaluate gender-related differences in drug dependence in treatment entry and to investigate how these differences may affect study participation, retention, and treatment response to better serve this population.

The construct and measurement equivalence of cocaine and opioid dependences: a National Drug Abuse Treatment Clinical Trials Network (CTN) study

INTRODUCTION

Although DSM-IV criteria are widely used in making diagnoses of substance use disorders, gaps exist regarding diagnosis classification, use of dependence criteria, and effects of measurement bias on diagnosis assessment. We examined the construct and measurement equivalence of diagnostic criteria for cocaine and opioid dependences, including whether each criterion maps onto the dependence construct, how well each criterion performs, how much information each contributes to a diagnosis, and whether symptom-endorsing is equivalent between demographic groups.

METHODS

Item response theory (IRT) and multiple indicators-multiple causes (MIMIC) modeling were performed on a sample of stimulant-using methadone maintenance patients enrolled in a multisite study of the National Drug Abuse Treatment Clinical Trials Network (CTN) (N=383). Participants were recruited from six community-based methadone maintenance treatment programs associated with the CTN and major U.S. providers. Cocaine and opioid dependences were assessed by DSM-IV Checklist.

RESULTS

IRT modeling showed that symptoms of cocaine and opioid dependences, respectively, were arrayed along a continuum of severity. All symptoms had moderate to high discrimination in distinguishing drug users between severity levels. "Withdrawal" identified the most severe symptom of the cocaine dependence continuum. MIMIC modeling revealed some support for measurement equivalence.

CONCLUSIONS

Study results suggest that self-reported symptoms of cocaine and opioid dependences and their underlying constructs can be measured appropriately among treatment-seeking polysubstance users.

An item response theory modeling of alcohol and marijuana dependences: a National Drug Abuse Treatment Clinical Trials Network study

OBJECTIVE

The aim of this study was to examine psychometric properties of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), diagnostics criteria for alcohol and marijuana dependences among 462 alcohol users and 311 marijuana users enrolled in two multisite trials of the National Drug Abuse Treatment Clinical Trials Network.

METHOD

Diagnostic questions were assessed by the DSM-IV checklist. Data were analyzed by the item response theory and the multiple indicators-multiple causes method procedures.

RESULTS

Criterion symptoms of alcohol and marijuana dependences exhibited a high level of internal consistency. All individual symptoms showed good discrimination in distinguishing alcohol or marijuana users between high and low severity levels of the continuum. In both groups, "withdrawal" appeared to measure the most severe symptom of the dependence continuum. There was little evidence of measurement nonequivalence in assessing symptoms of dependence by gender, age, race/ethnicity, and educational level.

CONCLUSIONS

These findings highlight the clinical utility of the DSM-IV checklist in assessing alcohol- and marijuana dependence syndromes among treatment-seeking substance users.

Brief buprenorphine detoxification for the treatment of prescription opioid dependence: a pilot study

We examined the feasibility of brief outpatient detoxification as a treatment for prescription opioid (PO) abusers. Fifteen PO-dependent adults were enrolled to receive buprenorphine stabilization, a 2-week buprenorphine taper, and subsequent naltrexone for those who completed the taper. Subjects also received behavioral therapy, urinalysis monitoring, and double-blind drug administration. Subjects provided 83.8%, 91.7% and 31.2% opioid-negative samples during stabilization, taper and naltrexone phases, respectively. Inspection of individual subject data revealed systematic differences in whether subjects successfully completed the taper without resumption of illicit opioid use. Post-hoc analyses were used to examine the characteristics of subjects who successfully completed the taper (Responders, n=5) vs. those who failed to do so (Nonresponders, n=9). These pilot data suggest a subset of PO abusers may respond to brief buprenorphine detoxification, though future efforts should aim to improve outcomes, investigate individual differences in treatment response and identify characteristics that may predict those for whom longer-term agonist treatment is warranted.

Item response theory analysis of DSM-IV cannabis abuse and dependence criteria in adolescents

OBJECTIVE

To examine three aspects of adolescent cannabis problems: do DSM-IV cannabis abuse and dependence criteria represent two different levels of severity of substance involvement, to what degree do each of the 11 abuse and dependence criteria assess adolescent cannabis problems, and do the DSM-IV items function similarly across different adolescent populations?

METHOD

We examined 5,587 adolescents ages 11 to 19, including 615 youths in treatment for substance use disorders, 179 adjudicated youths, and 4,793 youths from the community. All of the subjects were assessed with a structured diagnostic interview. Item response theory was used to analyze symptom endorsement patterns.

RESULTS

Abuse and dependence criteria were not found to represent different levels of severity of problem cannabis use in any of the samples. Among the 11 abuse and dependence criteria, problems cutting down and legal problems were the least informative for distinguishing problem users. Two dependence criteria and three of the four abuse criteria indicated different severities of cannabis problems across samples.

CONCLUSIONS

We found little evidence to support the idea that abuse and dependence are separate constructs for adolescent cannabis problems. Furthermore, certain abuse criteria may indicate severe substance problems, whereas specific dependence items may indicate less severe problems. The abuse items in particular need further study. These results have implications for the refinement of the current substance use disorder criteria for DSM-V.

Reliability of use, abuse, and dependence of four types of inhalants in adolescents and young adults

Inhalants, as a class of drugs, consists of heterogeneous substances that increase the probability of many serious illnesses and death. Research on inhalant abuse has lagged behind other drugs partly because of the need for a diagnostic instrument of different types of inhalants. This study was conducted to obtain reliability estimates for the new Substance Abuse Module DSM-IV inhalants diagnoses for four types of inhalants: aerosols, gases, nitrites, and solvents as well as different diagnostic configurations of inhalant-related criteria. Participants were 162 community sample adolescents or young adults (mean age=20.3 years, S.D.=2.4). Two-thirds of the sample was male and 83.3% was Caucasian. Kappas and intraclass correlation coefficients were computed to estimate test-retest reliabilities. Results suggested (a) abuse was more common than dependence (34.6% versus 12.3%), (b) reliabilities of abuse criteria and diagnosis were good to excellent across subtypes, and (c) reliabilities of dependence criteria and diagnoses were poor to good across subtypes. Alternative configurations of DSM-IV criteria that were consistent with previous research on adolescents provided excellent reliabilities across subtypes of inhalants. Moreover, 11.1% of participants experienced inhalants withdrawal.

The latent structure of marijuana and cocaine use disorders: results from the National Longitudinal Alcohol Epidemiologic Survey (NLAES)

To better understand the underlying concepts of substance dependence and abuse, the present study examines the factor structure of DSM-IV lifetime criteria for cannabis and cocaine use disorders. Data for this study were drawn from the National Longitudinal Alcohol Epidemiologic Survey (NLAES), a large nationally representative U.S. sample aged 18 years and older. Exploratory factor analysis (EFA) examined the factor structure for each substance and the factors were related to background covariates using latent variable modeling techniques. Separate analyses were conducted for lifetime marijuana and cocaine users. A two-factor solution was identified for each substance and was similar to DSM-IV abuse and dependence. The factors were highly correlated for both cannabis (r=0.73) and cocaine (r=0.77). Background variables accounted only for a modest amount of factor variance. In conjunction with the findings in alcohol use disorders, these results support the use of consistent criteria across substances in DSM-IV and ICD-10, and suggest that the consistent finding of two correlated factors across substances needs to be better understood.

A dimensional option for the diagnosis of substance dependence in DSM-V

In this paper we discuss the creation of dimensional equivalents for categorically defined substance use disorders (SUDs) in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V), which now is being created. We begin with a review of the considerable literature that has accumulated on the dimensional properties of the SUDs. These studies have primarily examined the alcohol use disorders, but work relevant to other substances is reviewed as well. The weight of evidence indicates that SUDs fit well into a unidimensional concept. We next discuss potential advantages, drawbacks, and challenges in developing a dimensional alternative for the SUDs and highlight some issues for an ongoing research agenda to further explore the challenges. Finally we offer a specific proposal for a SUDs dimensional option for DSM-V. The model we propose is based on, and would relate directly back to, the categorical criteria that will be created for the SUDs by the substance use diagnostic workgroup. It is our contention that offering a dimensional equivalent for the DSM-V categories would be of great value, but that the categorical and dimensional definitions should be based on the same symptoms and closely linked. A dimensional scale that does not relate directly to the categorical definition would be counterproductive.

Is there heterogeneity among syndromes of substance use disorder for illicit drugs?

The use of DSM criteria to evaluate liability to substance use disorders (SUDs) and to identify SUD phenotypes may not provide the sensitivity required to identify genes associated with vulnerability to SUDs. The purpose of this study is to evaluate a number of basic aspects of substance use that may be more proximal than full SUDs to risk genes, some of which may thus have greater potential utility as phenotypes in subsequent molecular genetic analyses. In this paper we present results from the first stage of our planned analyses, focusing on how individual symptoms of abuse and dependence may be used to create alternate phenotypes for SUDs. Specifically, we used factor analysis and biometrical modeling on each symptom of illicit substance abuse and dependence within different types of substances, and compared and contrasted factor patterns and heritabilities across the different substances. These analyses were carried out using a population-based sample of 3372 male-male twin pairs from the Vietnam Era Twin Registry who participated in the Harvard Twin Study of Substance Abuse. We obtained extensive data from these participants on substance use and SUDs via telephone interview in 1992, including data on the illicit substances: opiates, cocaine, cannabis, sedatives, stimulants, and psychedelics. The results indicate that: A) although a one-factor model assuming a single underlying liability for abuse and dependence symptoms and behaviors can be rejected for most substances, there is no uniform support for a two-factor model differentiating between abuse versus dependence; B) patterns of symptoms or behaviors reported by substance users vary across substances; C) not all symptoms or behaviors contribute equally to the presentation of an SUD; and D) the heritability of symptoms or behaviors of substance users varies both within and between substances. These results represent important first steps in facilitating the search for SUD-risk genes in subsequent high-throughput molecular genetic analyses by providing alternate phenotypes that may have both optimal validity and increased heritability.