Genetic relationship between the addiction diagnosis in adults and their childhood measure of addiction liability

The Concept of Resistance to Substance Use and a Research Approach: The Resist! Project

Illicit substance use is dangerous in both acute and chronic forms, frequently resulting in lethal poisoning, addiction, and other negative consequences. Similar to research in other psychiatric conditions, whose ultimate goal is to enable effective prevention and treatment, studies in substance use are focused on factors elevating the risk for the disorder. The rapid growth of the substance use problem despite the effort invested in fighting it, however, suggests the need in changing the research approach. Instead of attempting to identify risk factors, whose neutralization is often infeasible if not impossible, it may be more promising to systematically reverse the perspective to the factors enhancing the aspect of liability to disorder that shares the same dimension but is opposite to risk, that is, resistance to substance use. Resistance factors, which enable the majority of the population to remain unaffected despite the ubiquity of psychoactive substances, may be more amenable to translation. While the resistance aspect of liability is symmetric to risk, the resistance approach requires substantial changes in sampling (high-resistance rather than high-risk) and using quantitative indices of liability. This article provides an overview and a practical approach to research in resistance to substance use/addiction, currently implemented in a NIH-funded project. The project benefits from unique opportunities afforded by the data originating from two longitudinal twin studies, the Virginia Twin Study of Adolescent and Behavioral Development and the Minnesota Twin Family Study. The methodology described is also applicable to other psychiatric disorders.

The intermediary role of adolescent temperamental and behavioral traits on the prospective associations between polygenic risk and cannabis use among young adults of European Ancestry

BACKGROUND AND AIMS

Cannabis use (CU) is an etiologically complex behavior with several social, temperamental, neurocognitive, and behavioral precursors. Biometrical and molecular studies suggest an interplay of environmental and pleiotropic influences. However, it remains unclear whether identified genetic effects related to behavioral and temperamental characteristics have developmentally direct or indirect mechanisms on CU behavior. The Transmissible Liability Index (TLI) is a measure of continuous liability based on developmental precursors of substance use disorders. This study aimed to examine if the TLI plays a role in understanding genetic risk for CU behaviors.

DESIGN

Genome-wide association studies (n > 10 000; European Ancestry [EA]) of CU, risk tolerance, neuroticism, anxiety, and depression were used to construct polygenic scores (PGSs). Analyses assessed whether PGSs indirectly impacted risk for repeated use via TLI.

SETTING

United States of America.

PARTICIPANTS

From Add Health study, 4077 individuals of EA age 11 to 21 during baseline interview collection.

MEASUREMENTS

Outcomes were initiation and repeated cannabis use (>5× in lifetime). The TLI was parameterized using a latent factor from 21 questions assessing for precursors of disordered use.

FINDINGS

The marker-based heritability of TLI, initiation, and repeated use were significant, but modest (14%, P = 0.033; 15%, P = 0.025; and 17%, P = 0.008, respectively). TLI and repeated use were genetically correlated (r_g  = 0.76, P = 0.033). The PGS for CU was associated with increased risk for repeated use and PGS for risk tolerance and depression were associated with TLI. Mediation analyses indicated significant, but very weak, indirect effects of PGS for risk tolerance and depression on repeated CU via the TLI.

CONCLUSIONS

Adolescent behavioral and temperamental characteristics (i.e. the Transmissible Liability Index) appear to be early indicators of repeated cannabis use in adulthood. Although polygenic scores for cannabis use directly increased risk for repeated cannabis use, weak evidence was found for the role of polygenic scores of other internalizing/externalizing traits acting through adolescent derived Transmissible Liability Index on cannabis use behavior.

Adolescent Behavioral Characteristics Mediate Familial Effects on Alcohol Use and Problems in College-Bound Students

BACKGROUND

Studies suggest a broad spectrum of behaviors associated with drinking. Consequently, it is unclear whether patterns of familial risk for psychopathology are directly or indirectly related to patterns of alcohol use and problems in late adolescence or mediated by behavioral characteristics, such as temperament, mood.

OBJECTIVES

We examined direct and indirect effects of perceived family history of psychopathology on pre-collegiate alcohol use and problems via the Transmissible Liability Index (TLI).

METHODS

Participants (N = 302; 29.6% male) provided self-report data on age of onset of drinking, past 90-day frequency of alcohol use and problems (AUP), family history of internalizing and alcohol and illicit substance use, and TLI.

RESULTS

Approximately 21% of participants reported having at least one relative with a history of regular and/or problematic alcohol use, compared to 12% for illicit substance use, and -55% for internalizing problems. Higher TLI scores were associated with increased family history of substance use, alcohol use, and internalizing problems, as well as earlier age of onset of drinking. Family history of internalizing problems was the most robust indicator of AUP (β = 0.20 [95% CI = 0.04-0.36], P = .01). Path analyses suggested that the individual-level behaviors that comprise TLI mediate the effects of family history on age of initiation and regular alcohol consumption.

CONCLUSIONS

Family history of internalizing, drinking, and illicit substance use reflect generalized risk for a broad set of behaviors associated with risk for alcohol initiation and use during the transition from high school to college.

Forecasting Opioid Use Disorder at 25 Years of Age in 16-Year-Old Adolescents

OBJECTIVE

To evaluate the accuracy of detecting 16-year-old male (n = 465) and female (n = 162) youths who subsequently manifest opioid use disorder (OUD) at 25 years of age. We hypothesized that the combined measures of 2 components of etiology, heritable risk, and substance use, accurately detect youths who develop OUD.

STUDY DESIGN

Heritable risk was measured by the transmissible liability index (TLI). Severity of the prodrome presaging OUD was quantified by the revised Drug Use Screening Inventory containing the consumption frequency index (CFI) documenting substance use events during the past month and the overall problem density (OPD) score indicating co-occurring biopsychosocial problems. Diagnosis of OUD was formulated by a clinical committee based on results of the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition in conjunction with medical and social history records.

RESULTS

Bivariate analysis shows that the TLI, CFI, and OPD scores at 16 years of age predict OUD at 25 years. Multivariate modeling indicates that the TLI combined with the CFI predict OUD with 86% accuracy (sensitivity = 87%; specificity = 62%). The TLI and CFI at 16 years of age mediate the association between parental substance use disorder and OUD in offspring at 25 years of age, indicating that these measures respectively evaluate risk and prodrome.

CONCLUSIONS

These results demonstrate the feasibility of identifying youths requiring intervention to prevent OUD.

Risk for Substance Use Disorders in young adulthood: Associations with developmental experiences of homelessness, foster care, and adverse childhood experiences

BACKGROUND

Multiple developmental risk factors for Substance Use Disorders (SUDs) during young adulthood have been identified. In this investigation, we examined the impact of homelessness, foster care, and adverse childhood experiences (ACEs) prior to 12th grade on the development of three common SUDs during young adulthood-Alcohol Use Disorder (AUD), Tobacco Use Disorder (TUD) and Cannabis Use Disorder (CUD). Our hypothesis was that while both homelessness and ACEs are significant risk factors for young adult SUDs, foster care involvement might convey protection.

METHODS

Using nationally representative data from the National Longitudinal Study of Adolescent to Adult Health, measures of ACEs were derived from the CDC-Kaiser ACE study, and DSM-V SUD diagnoses were derived from items originally based on DSM-IV. SUD diagnoses were binned into "mild", "moderate", and "severe" groupings. Survey-based logistic models were used to estimate risks of SUDs while controlling for demographics.

RESULTS

The results suggest that the experience of homelessness prior to 12th grade in addition to ACEs were significantly associated with the development in young adulthood of the most severe forms of AUD and TUD and all severity levels of CUD. Foster care was not associated with either risk or protection from SUDs.

CONCLUSIONS

The experience of homelessness during development may be viewed as another detrimental ACE that is a risk factor for the most common SUDs in young adulthood. Given the magnitude of the current epidemic of homelessness in the U.S., these results should raise substantial concern.

Binge Eating Disorder (BED) in Relation to Addictive Behaviors and Personality Risk Factors

While there is good evidence that binge eating disorder (BED) is linked to higher-than-expected use of a broad range of addictive behaviors, mechanisms underlying this association are not well understood. Using a mediation-analytical approach with three age- and gender-matched groups – overweight/obese adults with (n = 42) and without (n = 104) BED, and normal-weight control participants (n = 73) – we tested the hypothesis that adults with BED would engage in more addictive behaviors and have higher scores on a personality-risk index than the two control groups. We also anticipated that the relationship between BED and addictive behaviors would be mediated by a high-risk personality profile. The predicted mediation effect was strongly supported. Contrary to expectation, BED participants did not engage in more addictive behaviors or have higher personality-risk scores than their weight-matched counterparts. However, both overweight/obese groups did have significantly higher scores than the normal-weight group. The relationships among personality risk, elevated body mass index (BMI), and addictive behaviors have important clinical implications, especially for treatments that target psycho-behavioral intervention for compulsive overeating and substance-use disorders.

Association of cognitive function and liability to addiction with childhood herpesvirus infections: A prospective cohort study

Liability to substance use disorder (SUD) is largely nonspecific to particular drugs and is related to behavior dysregulation, including reduced cognitive control. Recent data suggest that cognitive mechanisms may be influenced by exposure to neurotropic infections, such as human herpesviruses. In this study, serological evidence of exposure to human herpesvirus Herpes simplex virus Type 1 (HSV-1), cytomegalovirus (CMV), and Epstein-Barr virus (EBV) as well as Toxoplasma gondii was determined in childhood (age ~11 years) in 395 sons and 174 daughters of fathers with or without SUD. Its relationships with a cognitive characteristic (IQ) in childhood and with risk for SUD in adulthood were examined using correlation, regression, survival, and path analyses. Exposure to HSV-1, EBV, and T. gondii in males and females, and CMV in males, was associated with lower IQ. Independent of that relationship, EBV in females and possibly in males, and CMV and possibly HSV-1 in females were associated with elevated risk for SUD. Therefore, childhood neurotropic infections may influence cognitive development and risk for behavior disorders such as SUD. The results may point to new avenues for alleviating cognitive impairment and SUD risk.

Global white matter microstructural abnormalities associated with addiction liability score in drug naïve youth

Abnormalities in brain white matter (WM) structure have been reported in youths having a family history of substance use disorders (SUDs). It was hypothesized that these abnormalities constitute features of the liability for SUDs transmitted across generations. The association between severity of intergenerational risk for SUD, measured by the Transmissible Liability Index (TLI), and white matter microstructure was examined. Diffusion tensor imaging (DTI) measured WM microstructure in forty-four drug-naïve 10-14 year-olds (N = 19 with parental SUD). Metrics of WM microstructure (i.e., fractional anisotropy, radial diffusivity, mean diffusivity and axial diffusivity) were quantified across the whole brain and in four tracts of interest: anterior corona radiata, superior and inferior longitudinal fasciculi and superior fronto-occipital fasciculi. The TLI was completed by the youths, their parents and, when available, their teachers. The relationship between WM structure and TLI score across the entire group was evaluated using linear multiple regression and between group comparisons were also examined. Fractional anisotropy and radial diffusivity in multiple tracts across the brain were significantly associated with TLI scores. Confirming and extending prior research, the findings indicate that global atypicality in WM tracts was linearly related to liability for eventual SUD development in drug naïve youths.

Temperament disturbances measured in infancy progress to substance use disorder 20 years later

OBJECTIVE

This prospective study determined whether temperament before two years of age predicts transmissible risk for substance use disorder (SUD) up to a decade later and SUD outcome in adulthood.

METHOD

Boys between 10 and 12 years of age (N = 482) were tracked to age 22. The previously validated transmissible liability index (TLI) was administered at baseline, and temperament prior to two years of age was retrospectively rated. The Structured Clinical Interview for DSM-III-R (SCID) was administered to document presence/absence of SUD for parents at baseline and sons at age 22.

RESULTS

Path analysis revealed that number of parents with SUD predicted severity of temperament disturbance in their sons which in turn predicted TLI score at age 10-12, presaging SUD. Temperament before age two did not predict SUD at age 22. The association between number of SUD parents and transmissible risk was mediated by severity of temperament disturbance.

CONCLUSION

Temperament disturbance in early childhood, reflecting quality of behavioral and emotion regulation, comprise psychological antecedents of transmissible risk for SUD.

Item Response Theory Analysis to Assess Dimensionality of Substance Use Disorder Abuse and Dependence Symptoms

BACKGROUND

Item response theory (IRT) based studies conducted on diverse samples showed a single dominant factor for DSM-III-R and DSM-IV substance use disorder (SUD) abuse and dependence symptoms of alcohol, cannabis, sedative, cocaine, stimulants, and opiates use disorders. IRT provides the opportunity, within a person-centered framework, to accurately gauge each person's severity of disorder that, in turn, informs required intensiveness of treatment.

OBJECTIVES

The aim of this study was to determine whether the SUD symptoms indicate a unidimensional trait or instead need to be conceptualized and quantified as a multidimensional scale.

METHODS

The sample was composed of families of adult SUD+ men (n=349), and SUD+ women (n=173), who qualified for DSM-III-R diagnosis of substance use disorder (abuse or dependence) and families of adult men and women who did not qualify for a SUD diagnosis (SUD- men: n=190, SUD- women: n=133). An expanded version of the Structured Clinical Interview for DSM-III-R (SCID) was administered to characterize lifetime and current substance use disorders. Item response theory methodology was used to assess the dimensionality of DSM-III-R SUD abuse and dependence symptoms.

RESULTS

A bi-factor model provided the optimal representation of the factor structure of SUD symptoms in males and females. SUD symptoms are scalable as indicators of a single common factor, corresponding to general (non-drug-specific, common) liability to addiction, combined with drug-specific liabilities.

CONCLUSIONS

IRT methodology used to quantify the continuous general liability to addiction (GLA) latent trait in individuals having SUD symptoms was found effective for accurately measuring SUD severity in men and women. This may be helpful for person-centered medicine approaches to effectively address intensity of treatment.

Longitudinal Modeling of the Association Between Transmissible Risk, Affect During Drug Use and Development of Substance Use Disorder

OBJECTIVE

This longitudinal investigation examined the hypothesis that subjective experience during consumption of preferred drugs mediates the association of transmissible risk for substance use disorder (SUD) measured in childhood and adolescence, and SUD diagnosis in adulthood. Transmissible risk denotes the psychological characteristics having intergenerational continuity between parents and their biological children.

METHODS

The transmissible liability index (TLI) was administered to four hundred eighty-three 10 to 12-year-old boys (baseline). Follow-up evaluations were conducted when the boys attained 12-14, 16, 19, and 22 years of age, using age-specific versions of the TLI. Frequency of consumption of the participants' three most preferred drugs, affect on an ordinary day, affect while under influence of the preferred substances, and presence/absence of current SUD were assessed at 22 years of age.

RESULTS

Consumption frequency of preferred drugs among boys mediates the association of transmissible risk during childhood, and adolescence and SUD diagnosis in adulthood. Severity of negative affect on a drug-free day predicts frequency of consumption of preferred drugs, which, in turn, predicts severity of negative affect during the drug use event. Neither affect on a drug-free day nor affect during the drug use event mediates the association of transmissible risk and SUD.

CONCLUSIONS

Affect on drug-free days, and while under influence of preferred substances, covary with consumption frequency; however, affect is not related to transmissible SUD risk or SUD outcome.