Neuropsychology of dual diagnosis: Understanding the combined effects of schizophrenia and substance use disorders

Exploring Characteristics of Homicide Offenders With Schizophrenia Spectrum Disorders Via Machine Learning

The link between schizophrenia and homicide has long been the subject of research with significant impact on mental health policy, clinical practice, and public perception of people with psychiatric disorders. The present study investigates factors contributing to completed homicides committed by offenders diagnosed with schizophrenia referred to a Swiss forensic institution, using machine learning algorithms. Data were collected from 370 inpatients at the Centre for Inpatient Forensic Therapy at the Zurich University Hospital of Psychiatry. A total of 519 variables were explored to differentiate homicidal and other (violent and non-violent) offenders. The dataset was split employing variable filtering, model building, and selection embedded in a nested resampling approach. Ten factors regarding criminal and psychiatric history and clinical factors were identified to be influential in differentiating between homicidal and other offenders. Findings expand the research on influential factors for completed homicide in patients with schizophrenia. Limitations, clinical relevance, and future directions are discussed.

Independent associations and effect modification between lifetime substance use and recent mood disorder diagnosis with household food insecurity

Poor mental health and substance use are associated with food insecurity, however, their potential combined effects have not been studied. This study explored independent associations and effect modification between lifetime substance use and mood disorder in relation to food insecurity. Poisson regression analysis of data from British Columbia respondents (n = 13,450; 12 years+) in the 2007/08 Canadian Community Health Survey was conducted. Measures included The Household Food Security Survey Module (7.3% food insecure), recent diagnosis of a mood disorder (self-reported; 9.5%), lifetime use of cannabis, cocaine/crack, ecstasy, hallucinogens, and speed, any lifetime substance use, sociodemographic covariates, and the interaction terms of mood disorder by substance. For those with recent diagnosis of a mood disorder the prevalence of lifetime substance use ranged between 1.2 to 5.7% and were significantly higher than those without recent mood disorder diagnosis or lifetime use of substances (p’s < 0.05). For respondents with a recent mood disorder diagnosis or who used cannabis, food insecurity prevalence was higher compared to the general sample (p < 0.001); prevalence was lower for cocaine/crack use (p < 0.05). Significant effect modification was found between mood disorder with cannabis, ecstasy, hallucinogen and any substance use over the lifetime (PRs 0.51 to 0.64, p’s 0.022 to 0.001). Independent associations were found for cocaine/crack and speed use (PRs 1.68, p’s < 0.001) and mood disorder (PRs 2.02, p’s < 0.001). Based on these findings and the existing literature, future study about coping and resilience in the context of substance use, mental health, and food insecurity may lead to the development of relevant interventions aimed at mental well-being and food security.

Why do patients with psychosis use cannabis and are they ready to change their use?

Numerous studies have shown that patients with psychosis are more likely to use illicit drugs than the general population, with cannabis being the most popular. There exists overwhelming evidence that cannabis use can contribute to the onset of schizophrenia and poor outcome in patients with established psychosis. Therefore, understanding why patients use cannabis and whether they are motivated to change their habits is important. The evidence is that patients with psychosis use cannabis for the same reasons the general population does, to 'get high', relax and have fun. There is little support for the 'self-medication' hypothesis, while the literature points more towards an 'alleviation of dysphoria' model. There is a lack of research reporting on whether psychotic patients are ready to change their use of cannabis, which has obvious implications for identifying which treatment strategies are likely to be effective.

Management of schizophrenia with substance use disorders

Around 50% of patients with schizophrenia develop a co-occurring substance use disorder involving alcohol or illicit substances at some time during their lives. The comorbid substance abuse will markedly affect the course of illness of schizophrenia. In this article, the authors review the epidemiology, theories of causation, effect on the course of illness, and treatment of co-occurring schizophrenia and substance use disorder.

Homers regulate drug-induced neuroplasticity: implications for addiction

Drug addiction is a chronic, relapsing disorder, characterized by an uncontrollable motivation to seek and use drugs. Converging clinical and preclinical observations implicate pathologies within the corticolimbic glutamate system in the genetic predisposition to, and the development of, an addicted phenotype. Such observations pose cellular factors regulating glutamate transmission as likely molecular candidates in the etiology of addiction. Members of the Homer family of proteins regulate signal transduction through, and the trafficking of, glutamate receptors, as well as maintain and regulate extracellular glutamate levels in corticolimbic brain regions. This review summarizes the existing data implicating the Homer family of protein in acute behavioral and neurochemical sensitivity to drugs of abuse, the development of drug-induced neuroplasticity, as well as other behavioral and cognitive pathologies associated with an addicted state.

The neuropsychology of cannabis and other substance use in schizophrenia: review of the literature and critical evaluation of methodological issues

Research on the neuropsychology of substance use in schizophrenia has been steadily growing over the past decade. However, significant gaps remain in the knowledge of individual substances and their relationship to cognition in the schizophrenia spectrum disorders. Approximately 65 studies to date have directly examined this relationship. Of these, approximately 20 have focused on nicotine, 15 on alcohol, 10 on cocaine, three on stimulants/hallucinogens, one on benzodiazepines, 10 on polydrug abuse, and seven on cannabis. Research on cannabis is especially lacking, given that worldwide it is the most commonly used illicit drug in schizophrenia, is used at higher rates in schizophrenia than in the general population, and makes its own unique contribution to the onset and prognosis of schizophrenia. In the present paper an overview of the neuropsychology literature on substance use in schizophrenia is presented, with special emphasis on cannabis. This incorporates a discussion of the methodological limitations inherent in these studies, and range of potential confounding variables that were not considered or controlled, providing directions for future research into the cognitive correlates of cannabis and other substance use in schizophrenia.

Assessment of motivation to change substance use in dually-diagnosed schizophrenia patients

Assessment of motivation to change substance use can be helpful in evaluating treatment readiness and outcome. However, the utility of self-report measures of motivation with schizophrenia patients is questionable. In the current study patients with schizophrenia and either concurrent cocaine dependence or remitted dependence completed the University of Rhode Island Change Assessment-Maryland (URICA-M), a self-report inventory that assesses motivation, and an analogous cartoon instrument at baseline and 6-months follow-up. Results demonstrate that the cartoon readiness to change score was related to increased treatment utilization and decreased substance use; results were not as favorable for the URICA-M. Findings suggest that the cartoon measure may be a suitable alternative to assess motivation to change substance use with cognitively impaired patients.

Comorbid substance abuse and neurocognitive function in recent-onset schizophrenia

Despite the high prevalence of comorbid substance use disorder (SUD) up to 65% in schizophrenia there is still few knowledge about the influence of substance abuse on neurocognitive function. In a prospective design we recruited 68 patients (aged 18-40 years) diagnosed as recent-onset schizophrenia or schizoaffective disorder consecutively admitted to hospital. The patients received standardized psychopathological evaluation of schizophrenic symptoms [Brief Psychiatric Rating Scale (BPRS), Scale for the Assessment of Negative Symptoms (SANS)], depressive symptoms [Montgomery Asberg Depression Rating Scale, (MADRS)] and global ratings [Clinical Global Impressions Scale (CGI), Global Assessment of Functioning Scale (GAF)]. Out of this sample 44 subjects underwent after stabilization (4-6 weeks after admission) neuropsychological investigation focusing on early information processing (Trail-Making-Test A, Digit Span), visuo-spatial ability (Corsi Block Tapping), verbal fluency (Verbal Fluency Test, semantic and letter category), and executive functioning and cognitive flexibility [Trail-Making-Test B, Wisconsin Card Sorting Test (WCST)]. About 36% of patients reported drug abuse [European Addiction Severity Index (EuropASI)] with a high prevalence for cannabis. Compared with nonabusers the sample of substance abusers was younger, predominantly male and had lower socioeconomic status. Attentional impairment according to the SANS subscale was less in abusers than in nonabusers on admission, no other psychopathological differences could be detected. Schizophrenic patients without substance abuse demonstrated significantly better performance only in a few neurocognitive tasks (Verbal Fluency, letter category and at trend level Digit Span, backwards), while there tended to be an advantage for substance abusers in executive functioning (WCST, not significant). These results are consistent with other studies of first-episode patients. The lack of higher cognitive disturbance in young schizophrenic patients with comorbid substance abuse may encourage clinicians to develop integrated treatment programmes using cognitive strategies of drug therapy.

Comorbid schizophrenia and substance abuse: a review of epidemiology and course

Over the last dozen years, our knowledge regarding comorbid schizophrenia (SCZ) and substance use disorder (SUD) has evolved in several ways. First, the rate of lifetime comorbid SCZ-SUD appears to have increased another 20-30%, so now about 70-80% of persons with SCZ have lifetime SUD. Second, early remission of SUD has become commonplace among patients with SCZ, perhaps outnumbering the number of SCZ-only patients as well as those with active SCZ-SUD. Third, sustained SUD remission is well demonstrated, though the rates may yet be low. Fourth, research on comorbid SCZ-SUD is filling out our knowledge in many areas, including the characteristics of SCZ patients at risk for SUD, reasons SCZ patients seek out substances, effects of various substances on SCZ course and symptoms, and obstacles to SUD recovery in people with SCZ. The influence of SUD treatment and self-help on epidemiology and course has not been adequately evaluated. Primary prevention and early treatment of SUD in SCZ patients are still relatively neglected, though they offer our greatest hope for enhancing the lives of people with SCZ and improving the cost efficacy of care.

Reasons for increased substance use in psychosis

Around half of all patients with schizophrenia are thought to abuse drugs or alcohol and there is good evidence to suggest that they have poorer outcomes than their non substance using counterparts. However, despite more than twenty years of research there is still no consensus on the aetiology of increased rates of substance use in people with psychosis. There is a clear need to understand the reasons for such high rates of substance use if treatments designed to help patients abstain from substance use are to be successful. This paper provides an update of the literature examining the reasons for substance use by people with psychosis, and includes a comprehensive review of the self report literature. The main theories as to why people with psychosis use substances are presented. There is evidence to suggest that cannabis may have a causal role in the development of psychopathology but not for other substances. The self report literature provides support for an 'alleviation of dysphoria' model of substance use but there is little empirical support for the self medication hypothesis, or for common factor models and bidirectional models of comorbidity. It is likely that there are multiple risk factors involved in substance use in psychosis and more work to develop and test multiple risk factor models is required.

Development of a comprehensive measure to assess clinical issues in dual diagnosis patients: The Substance Use Event Survey for Severe Mental Illness

This paper provides a description of The Substance Use Event Survey for Severe Mental Illness (SUESS), a brief (20-30 min) interview that assesses clinical issues and domains that are relevant patients with substance use disorders and severe mental illness. First, we discuss the need for a new clinical measure for dual diagnosis patients, as well as our process of creating domains and items and developing the content of the assessment. Second, we provide a first look at the performance of the SUESS in a large sample of dually diagnosed patients from several large scale studies, including how patients responded to the instrument and their ability to complete the items. Third, we present initial reliability data on the SUESS. Finally, we include some initial validity data, including comparison of the self-report of substance use questions to urinalysis results, and verification of the service use information from medical record review. The SUESS appears to be a useful assessment that is tolerated and understood by dual diagnosis patients, and shows good preliminary reliability and validity.

Executive function and memory in relation to olfactory deficits in alcohol-dependent patients

BACKGROUND

Prior research indicates that chronic alcoholism is accompanied by olfactory deficits. These have been suggested to reflect dysfunctions in olfactory brain regions. The present study investigated the role of neurocognitive functioning in tests (executive function and memory) sensitive to the functional integrity of brain areas that are crucial to olfactory processing in patients with alcohol dependence.

METHODS

Performance on olfactory functions (detection threshold, quality discrimination, identification), executive function (Wisconsin Card Sorting Test), and memory (German version of the California Verbal Learning Test) was assessed in 32 alcohol-dependent patients and 30 healthy comparison subjects, comparable in age, gender, and smoking status.

RESULTS

Compared with controls, alcohol-dependent patients were impaired in all 3 domains, olfactory functions, executive function, and memory. In patients, olfactory discrimination ability was positively correlated with executive function performance. Regression analyses conducted to clarify the relation between group (patients vs controls), executive function, memory, and olfactory functions indicated that group was the only significant predictor of olfactory detection threshold and identification, and both group and executive function were found to be the significant predictors of olfactory discrimination.

CONCLUSIONS

Olfactory deficits in alcohol dependence appear to be associated with prefrontal cognitive dysfunction. Results indicate that olfactory quality discrimination deficits are related to executive function impairment. These findings add to the available research on frontal lobe dysfunction in alcoholism, suggesting that alcohol-related olfactory discrimination deficits may be associated with impairment in the functional integrity of the prefrontal lobe.

Correlates of substance use disorder among psychiatric outpatients: focus on cognition, social role functioning, and psychiatric status

This study compared psychiatric outpatients who were never, former, and current substance abusers on psychiatric, social, and cognitive functioning. Fifty-six outpatients with schizophrenia spectrum and bipolar disorders volunteered to complete diagnostic and social role function interviews, self-report inventories, and neuropsychological tests. Multinomial logit regression analyses indicated that current and former abusers reported greater subjective feelings of distress than those who never abused. Contrary to expectations, however, both groups of substance abusers performed better on nonverbal cognitive tests compared with those who never abused. Differences in social functioning were also observed: former abusers demonstrated better instrumental role functioning than those who never abused. This pattern of findings challenges assumptions about additive effects of comorbid disorders on cognitive and social functioning.

Treating substance abuse in schizophrenia. An initial report

Schizophrenia patients show alarmingly high rates of substance use disorders. These patients experience neurocognitive and social deficits that make it difficult for them to benefit from effective treatment strategies designed for less-impaired populations. Previously, we described Behavioral Treatment for Substance Abuse in Schizophrenia and discussed how the program was adapted for this population. Here we provide an update of BTSAS, discuss our clinical experience running the intervention, and review how it has changed over five years of development. We present attendance, participation, and substance use data on patients who consented to attend (n = 42), completed (n=14), and dropped out (n = 14) of the program. Outcome data are provided for 14 patients, and comparisons are made between good (n = 5; > or = 67% of urine tests clean from a goal drug over 6 months) and poor (n = 9; < or = 66% of urine tests clean) progress patients. Implications for the treatment are discussed.

Anticholinergicity and cognitive processing in chronic schizophrenia

Patients with chronic schizophrenia suffer from alterations in cholinergic functioning due to several factors, including the disease diathesis and pharmacologic treatments. Acetylcholine-cognition relationships are well explored in normals but are unclear in schizophrenia. Prior work indicated serum anticholinergicity does not cause global cognitive impairment in this group (Tracy et al., 1998a), raising the possibility that anticholinergicity normalizes an abnormal hyperactive cholinergic state. Serum anticholinergic levels were determined in 38 chronic schizophrenia patients using an established radioreceptor assay method. Six cognitive functions associated with cholinergic tone in normals were tested. The potential role of autonomic arousal and cigarette smoking were also assessed as both have been linked to cholinergic functioning. Regression analyses showed measures of inhibitory executive control and effortful memory accounted for a greater proportion of the variance in the anticholinergicity measure compared to the other variables. The data demonstrate a relationship between high anticholinergicity and worse performance on two types of attention-resource demanding cognitive processes and do not support the notion that reduced cholinergic tone normalizes a hyperactive cortical acetylcholine substrate. Relevant neuroanatomic structures and implications for models of cognitive deficits in schizophrenia are discussed.

Drug-use behavior and correlates in people with schizophrenia

This study examined how illicit drugs were accessed, reasons for drug use, prevalence of emotional, physical, and sexual abuse, psychiatric symptomatology, level of functioning, and the relationship of these factors to substance use in 25 schizophrenia outpatients. To identify unique substance-use behaviors or correlates, this information was compared to 25 substance-abusing outpatients with major affective disorders, and 30 people with schizophrenia alone. Patients largely financed their drug habits with money given by immediate family members, and reported using drugs primarily for social reasons. While all three groups reported high levels of physical, sexual, and emotional abuse, a relationship between emotional abuse and substance use was observed only for people with schizophrenia. There were no differences between the two schizophrenia groups in psychiatric symptoms or level of functioning. The treatment implications of these findings are discussed.

Learning and memory impairment in cocaine-dependent and comorbid schizophrenic patients

Impairments in verbal learning and memory functioning have been found to be cardinal features among individuals with schizophrenia as well as among non-schizophrenic cocaine abusers. Cognitive deficits in these areas, moreover, have been associated with poor treatment response and short-term outcome. Little is known, however, about the acute effects of cocaine abuse on schizophrenic patients' learning and memory functioning. Consequently, a potentially reversible and treatable source of cognitive impairment has been virtually ignored. The present study examined the extent of verbal learning and memory impairment in a group of cocaine-dependent schizophrenic patients (n=42) and a group of non-schizophrenic cocaine-dependent patients (n=21) within 72 h of the last cocaine use using the California Verbal Learning Test (CVLT). Schizophrenic patients (n=34) without any substance-use disorders were also tested in an identical time frame and served as a comparison group. Results revealed that all groups demonstrated significant learning and memory impairment relative to CVLT published age and gender corrected norms. Both cocaine-dependent and non-substance abusing schizophrenic groups presented a very similar pattern of impaired learning and recall performance across all CVLT task domains. Comorbid patients, in contrast, presented with marked deficits in their ability to learn and recall verbal information relative to either schizophrenic or cocaine-only groups. Moreover, the cocaine-abusing schizophrenic patients showed significant forgetfulness of the information that they did acquire during delayed recall conditions. The performance deficits exhibited by cocaine-abusing schizophrenic patients differed not only in relative severity of impairment, but also qualitatively in their increased rates of forgetfulness of acquired information. These results are interpreted in terms of the neurobiological substrates of learning and memory and the neurobiological impact of cocaine on schizophrenic patients' cognition during the early phase of inpatient hospitalization. These results suggest that comorbid patients should be targeted for specialized remediation efforts at the beginning phases of inpatient treatment.

Neurocognitive dysfunction in dually-diagnosed patients: a potential roadblock to motivating behavior change

Substance abuse has been associated with cognitive dysfunction, such as problems with attention, reasoning, and memory. Certain psychiatric disorders also have been associated with cognitive difficulties, thus placing dually-diagnosed patients at high risk for cognitive impairment that could interfere with successful entry into or completion of therapy. Twenty-two dually-disordered inpatients were administered the Brief Readiness to Change Questionnaire to measure levels of motivation to change substance use, and a neuropsychological test battery that included the Wechsler Adult Intelligence Scale-Revised (WAIS-R), the Halstead Category Test (HCT), and the Wechsler Memory Scale-Revised (WMS-R). Higher general intellectual, executive, and memory functioning were significantly related to greater scores in readiness to change substance abuse in this sample. Cognitive ability may be an important variable to consider in the motivation and treatment of dually-diagnosed patients.

Substance abuse treatment for people with schizophrenia

Substance abuse by people with schizophrenia is a serious public health problem that is associated with poor treatment compliance, increased rates of relapse, and disruption of role functioning. There is widespread agreement on the need to integrate psychiatric and substance abuse treatment for this dual disorder, but to date there are no specific treatments with solid empirical support. We first review the primary consequences of substance abuse by people with schizophrenia and then examine what is currently known about their treatment needs. We then describe the special problems faced by this population that interfere with their ability to reduce substance use, with or without treatment. The remainder of the paper focuses on description of a new behavioral treatment we have developed to compensate for the cognitive and motivational deficits that characterize the illness. We describe the development process and present some process data that demonstrate that the intervention is safe and acceptable for people with schizophrenia, and that we are able to train therapists to administer the procedures in a consistent and effective manner. Future studies will examine the effectiveness of the intervention.

Information-processing characteristics of explicit time estimation by patients with schizophrenia and normal controls

The information-processing characteristics of time estimation have not been well-documented. This research investigated explicit time estimation to test whether (1) it can occur "automatically" and (2) the cognitive function generally known as "working memory" predicts accuracy of time estimation. Data on two tasks requiring explicit time judgement (time interval estimation and production) are reported for a sample of 43 normal, healthy controls and 19 inpatients with chronic schizophrenia. Each task was given in a standard (passing time interval is unfilled) and dual-task format (interval is filled by oral reading). Multivariate analysis of variance suggested that for both patients' and the normal controls' time estimation accuracy was (1) highly sensitive to whether a passing interval was filled with a concurrent activity such as reading and (2) predictable on the basis of age, education, and working memory skills. Also, the effect of the dual-task manipulation did vary as a function of psychosis for the Time Interval Production task. The data suggest that procedures for explicit time judgements do not occur automatically and utilize controlled processes such as working memory.

Complications of severe mental illness related to alcohol and drug use disorders

In this chapter we review research on the relationships between substance use disorder and 11 domains of adjustment for people with severe mental illness. Studies are divided into correlational research and prospective, longitudinal research, with greater weight given to those in the latter category. The weight of the evidence indicates that substance abuse severely complicates severe mental illness in the following domains: relapse of psychiatric illness, hospitalization, disruptive behavior, familial problems, residential instability, decreased functional status, HIV infection, and medication noncompliance. We discuss the limits of causal inference in these studies and the possible mechanisms that relate substance abuse to various complications.