Cognitive disparity in schizophrenics with and without cocaine dependency

Cognitive and functional deficits in people with schizophrenia: Evidence for accelerated or exaggerated aging?

Cognitive and functional deficits are commonly seen in people with schizophrenia. The profile of these impairments has a resemblance to the cognitive changes seen in healthy aging. In specific, many of the cognitive ability domains that change the most with aging in healthy people are the most salient of these deficits seen in people with schizophrenia, including prominent deficits in processing speed, working memory, and episodic memory. Functional deficits seen in schizophrenia are also similar to those seen in healthy aging. There is a relationship between multiple psychotic relapses and treatment resistance and longitudinal cognitive and functional changes in schizophrenia, with this relationship starting early in the course of illness. Cognitive performance in people with schizophrenia may be consistent with accelerated or premature aging. People with schizophrenia perform similarly to healthy people who are 3 or more decades older on indices of both cognition and their everyday functional skills. Some people with schizophrenia show exaggerated cognitive changes as well. Cognitive and functional performance worsens at the outset of the illness in schizophrenia compared to premorbid functioning, meaning that these deficits are not due to development disabilities. There are multiple medical and substance abuse comorbidities in schizophrenia and although these comorbidities affect cognitive functioning, they are not completely responsible for age-related changes.

Evaluating the relationship between cannabis use and IQ in youth and young adults at clinical high risk of psychosis

Among people with psychosis, those with a history of cannabis use show better cognitive performance than those who are cannabis naïve. It is unknown whether this pattern is present in youth at clinical high risk (CHR) of psychosis. We evaluated relationships between IQ and cannabis use while controlling for use of other substances known to impact cognition in 678 CHR and 263 healthy control (HC) participants. IQ was estimated using the Vocabulary and Block Design subtests of the Wechsler Abbreviated Scale of Intelligence. Drug and alcohol use severity and frequency were assessed with the Alcohol and Drug Use Scale, and we inquired participants' age at first use. CHR were further separated into early and late age at onset of cannabis use sub-groups, and low-, moderate- and high-frequency sub-groups. No significant differences in IQ emerged between CHR or HC cannabis users vs. non-users, or between use frequency groups. CHR late-onset users showed significantly higher IQ than CHR early-onset users. Age at onset of cannabis use was significantly and positively correlated with IQ in CHR only. Results suggest that age at onset of cannabis may be a more important factor for IQ than use current use or use frequency in CHR.

Cognitive functioning associated with stimulant use in patients with non-affective psychosis, their unaffected siblings and healthy controls

BACKGROUND

Little is known about the effect of stimulant use (amphetamines, cocaine, ecstasy) on cognitive functioning in schizophrenia patients. The current study examined (1) whether recency and frequency of stimulant use is associated with cognitive functioning and (2) whether these associations differ between psychotic patients, their unaffected siblings and controls.

METHOD

Participants completed a comprehensive cognitive test battery. Stimulant use was assessed by urinalysis and by the Composite International Diagnostic Interview (CIDI). Using random effects regression models, the main effects of Stimulant Use and the interaction with Diagnostic Status on cognitive functioning were assessed.

RESULTS

The interaction term between Stimulant Use and Diagnostic Status was not significant for any of the cognitive outcome variables, indicating similar effects of stimulant use in all three groups. Recent stimulant users showed more errors deficit in verbal learning in comparison to never users (Cohen's d = -0.60, p < 0.005). Lifetime frequent stimulant use was significantly associated with worse immediate and delayed verbal recall, working memory and acquired knowledge (Cohen's d = -0.22 to -0.29, p < 0.005). Lifetime infrequent stimulant use was not associated with significant cognitive alterations in comparison to never use.

CONCLUSIONS

The presence of cognitive deficits associated with lifetime stimulant use is dependent on the frequency of use, with no observed deficits in infrequent users and modest negative effects in frequent users.

Lifetime cannabis use and cognition in patients with schizophrenia spectrum disorders and their unaffected siblings

The relationship between cannabis and cognitive performance is controversial. While both acute administration and long-term cannabis use impair cognitive performance in healthy subjects, several studies have shown improved cognitive outcomes in patients with schizophrenia spectrum disorders who use cannabis. The aim of this study was to determine the relationship between lifetime cannabis use, as assessed longitudinally over 10 years of follow-up in a sample of 42 patients and 35 of their unaffected siblings, and current cognitive performance. Forty-two healthy control subjects were assessed at follow-up with the same instruments. Stepwise linear regression revealed a negative effect of longitudinal cannabis use on performance in a social cognition task in the patient group. In the sibling group, lifetime cannabis use had a negative effect on processing speed and declarative memory performance. In the control group, cannabis use per se did not predict cognitive performance; however, when adding lifetime tobacco use to the model, we found a negative association between lifetime cannabis and tobacco use and processing speed and social cognition performance. Moreover, a lower IQ associated with current cannabis use predicted worse attentional performance in the control group. The differential pattern of associations between cannabis use and cognitive performance in patients compared with siblings and controls can be explained by the negative impact of illness on cognition.

Comorbid substance use disorder in schizophrenia: a selective overview of neurobiological and cognitive underpinnings

Although individuals with schizophrenia show a lifetime prevalence of 50% for suffering from a comorbid substance use disorder, substance abuse usually represents an exclusion criterion for studies on schizophrenia. This implies that surprisingly little is known about a large group of patients who are particularly difficult to treat. The aim of the present work is to provide a brief and non-exhaustive overview of the current knowledgebase about neurobiological and cognitive underpinnings for dual diagnosis schizophrenia patients. Studies published within the last 20 years were considered using computerized search engines. The focus was on nicotine, caffeine, alcohol, cannabis and cocaine being among the most common substances of abuse. All drugs of abuse target dopaminergic, glutamatergic and GABAergic transmission which are also involved in the pathophysiology of schizophrenia. Current literature suggests that neurocognitive function might beless disrupted in substance-abusing compared to non-abusing schizophrenia patients, but in particular the neuroimaging database on this topic is sparse. Detrimental effects on brain structure and function were shown for patients for whom alcohol is the main substance of abuse. It is as yet unclear whether this finding might be an artifact of age differences of patient subgroups with different substance abuse patterns. More research is warranted on the specific neurocognitive underpinnings of schizophrenia patients abusing distinct psychoactive substances. Treatment programs might either benefit from preserved cognitive function as a resource or specifically target cognitive impairment in different subgroups of addicted schizophrenia patients.

Neuropsychological functioning and age-related changes in schizophrenia and/or cocaine dependence

Although little is known about the combined effects of Schizophrenia (SZ) and Substance Use Dependence (SUD) in neurocognitive functioning, the current literature points out that performance depends on the specific cognitive domains, the age of individuals and the type of substance of abuse. Our aim is to elucidate, in a sample with SZ and/or cocaine dependent individuals in remission for more than 4 months, their performance in attention, verbal memory and speed of processing, taking into account the possible effect of both age and duration of SUD. The total sample consisted of 95 male patients, aged 20 to 60 years, divided in three groups: one group with SZ and cocaine dependence (SZ+), another group with SZ without cocaine dependence (SZ-) and a third group with cocaine dependence without psychiatric comorbidity (COC). Our results show that those SZ+ who were abstinent for more than four months did not differ from their SZ- counterparts in the neuropsychological functioning. Both SZ groups performed significantly worse than the COC group. A negative impact of age on the neuropsychological performance was found in the SZ+ group, suggesting additive later cognitive deficits in SZ+ patients due to the long-term brain damage of SUD.

Executive functioning in individuals with schizophrenia and/or cocaine dependence

OBJECTIVE

Although little is known about neurocognition in Dual Diagnosis, it has been suggested that Schizophrenia (SZ) patients with comorbid substance use belong to a subgroup with lower genetic vulnerability to develop SZ and, consequently, they show better executive and social premorbid functioning. The first aim of this study was to assess the executive functioning, and the second one was to explore the effect of age of onset of substance use in neurocognition in SZ patients with cocaine dependence.

METHODS

The total sample consisted of 95 male patients, aged 20 to 60 years, divided in three groups: one group with SZ and cocaine dependence (SZ+; n = 30), another group with SZ without cocaine dependence (SZ-; n = 30), and a control group with cocaine dependence without psychiatric comorbidity (COC; n = 35).

RESULTS

We found a better executive functioning in both SZ+ and COC than SZ-. We observed a worse performance of SZ+ patients compared with COC in cognitive set-shifting regardless the age of onset of consumption.

CONCLUSIONS

The results agree with the hypothesis of a lower genetic vulnerability in SZ+ patients to develop psychosis compared with SZ-, who develop it without any additional trigger. However, future research is needed to clarify the current knowledge gaps.

Assessing executive and community functioning among homeless persons with substance use disorders using the executive function performance test

This study investigates the utility of an occupational therapy assessment of executive and performance functioning and indicators of community adjustment among adults with histories of homelessness and substance abuse. A sample of 60 individuals living in a supported housing programme was interviewed about community living experiences and was assessed using the Executive Function Performance Test (EFPT). A descriptive and correlational study design was used. Measurable levels of cognitive and task impairment were documented, in older adults, non-US citizens and those diagnosed with cognitive impairments. Those who had completed a supported education/employment programme (Total EFPT t = -2.83, 0.008) performed better as did those who were employed (Total EFPT t = -2.33, 0.03), met regularly with their case managers (cooking t = -2.07, 0.04), had hobbies (paying bills r = -0.31, 0.02) and had longer periods of abstinence (organization/planning t = -3.59, 0.001). Limitations of the study include the unanticipated need by the clients for additional translation services. Future directions include a randomized controlled intervention study using the EFPT. An implication of this study for occupational therapists working with homeless clients who abuse substances is the importance of assessing and treating their cognitive impairments as well as providing these services within housing first agencies.

Neurocognitive characteristics of individuals with schizophrenia and cocaine dependence: comparison of currently dependent and remitted groups

Several investigations of cognitive functioning in individuals with schizophrenia and co-occurring cocaine use have yielded mixed results when compared with samples with schizophrenia only. However, no studies have specifically compared remitted and current cocaine dependence in schizophrenia. Such an analysis could help clarify the degree and type of cognitive impairment associated with cocaine dependence in schizophrenia. Two samples of individuals with schizophrenia - those with current cocaine dependence (n = 72) and those with cocaine dependence in remission (n = 48) were compared on a brief neuropsychological test battery. Parallel current dependent and remitted samples with affective disorder (n = 65 and n = 55) were also included in the analyses. Results yielded few neuropsychological differences between remitted and current dependent states across the SZ and AD groups. These findings suggest that cognitive impairment may be relatively static in these populations.

Contradictory cognitive capacities among substance-abusing patients with schizophrenia: a meta-analysis

Although a substance use disorder (SUD) is traditionally associated with psycho-bio-social impairments, recent investigations among persons with schizophrenia (Sz) generated divergent results. Certain persons with Sz+SUD might in fact present better social and cognitive functioning than persons with Sz without SUD. This meta-analysis was conducted to verify this counterintuitive possibility and to determine whether factors such as substance type, severity or nature of psychotic symptoms and age of the patients help discriminate these subgroups. Twenty-three studies met the inclusion criteria and data from 1807 persons with schizophrenia, with or without comorbid SUD, were available for analyses. As a group, persons with Sz+SUD did not obtain significantly higher scores at a Global Cognitive Index than persons with Sz without SUD, although they were better at the Trail Making Task and the speed processing domain. Secondary analyses showed the importance of considering intermediate factors, particularly the preferred substance used and the mean age. While consumption of alcohol was associated with a global cognitive scores similar to that of persons with Sz without an SUD and lower working memory capacities, preferential use of cannabis was instead associated with higher scores for problem solving and reasoning and visual memory. Age was inversely related to the size of the effects. It is concluded that previous mixed results obtained with cognitive evaluations of persons with Sz+SUD might reflect the heterogeneity of participants and that subgroups of patients might be defined on the basis of intermediate factors.

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.