Does a history of cannabis use influence onset and course of schizophrenia?

INTRODUCTION: While evidence strongly supports a causal effect of cannabis on psychosis, it is less clear whether the symptom pattern, clinical course, and outcomes differ in cases of schizophrenia with and without a background of cannabis use. METHODS: Analysis of medical records from a longitudinal follow-up of Swedish conscripts with data on cannabis use in adolescence and subsequent incidence of schizophrenia. One hundred sixty patients with schizophrenia were assessed using the OPCRIT protocol. Cases were validated for diagnosis schizophrenia according to OPCRIT. RESULTS: Patients with a cannabis history (n = 32), compared to those without (n = 128), had an earlier age at onset, a higher number of hospital admissions and a higher total number of hospital days. There was no significant difference in type of onset and clinical symptom profiles between the groups. CONCLUSION: Our findings indicate that the disease burden of schizophrenia is greater in individuals who use cannabis during adolescence. Strengthening evidence on causality and teasing out long-term effects of pre-illness cannabis use from continued post-illness has clinical implications for improving schizophrenia outcomes.

Alcohol use disorders and risk of Parkinson's disease: findings from a Swedish national cohort study 1972-2008.

BACKGROUND: Alcohol has been suggested to be either protective of, or not associated with Parkinson's disease (PD). However, experimental animal studies indicate that chronic heavy alcohol consumption may have dopamine neurotoxic effects relevant for PD. We studied the association between diagnosed alcohol use disorders and PD. METHODS: All individuals in Sweden admitted with a diagnosis of an alcohol use disorder or appendicitis (reference group) between January 1, 1972 and December 31, 2008 were identified through the Swedish National Inpatient Register, and followed for up to 37 years for a diagnosis of PD. We estimated hazard ratios (HR) with 95% confidence intervals (CI) and adjusted for age and sex. RESULTS: We found 1,741 (0.3%) cases of PD in the cohort of 602,930 individuals, 1,083 (0.4%) among those admitted with an alcohol use disorder and 658 (0.2%) of the individuals admitted with appendicitis. The mean follow-up time was 13.6 and 17.1 years, respectively. The HR for PD associated with an alcohol use disorder was 1.38 (CI 1.25-1.53) adjusted for age and sex. When the risk was estimated in age groups for first hospital admission with PD the highest risk was observed in the lowest age group, ≤44, HR 2.39 (0.96-5.93), adjusted for age at exposure and sex. CONCLUSIONS: A history of an alcohol use disorder conferred an increased risk of admission with a diagnosis of Parkinson's disease in both women and men. In particular, the risk seemed higher at lower ages of first admission with Parkinson's disease.

Infections in the CNS during childhood and the risk of subsequent psychotic illness: a cohort study of more than one million Swedish subjects.

OBJECTIVE: Infections during early life have been suggested to play a role in the etiology of schizophrenia. Most studies have focused on fetal life; few have explored risk associated with infection during childhood. The results of these have been inconsistent. The present study aims to investigate whether there is an increased risk of schizophrenia and other nonaffective psychoses associated with viral or bacterial CNS infections during childhood and, if so, which specific agents are involved. METHOD: A national cohort consisting of 1.2 million children born between 1973 and 1985 was followed up by using Swedish national registers to retrieve data on hospital admissions for CNS infections at 0-12 years of age (bacterial: N=2,435, viral: N=6,550) as well as admissions for nonaffective psychotic illnesses from the 14th birthday (N=2,269). RESULTS: There was a slightly increased risk of nonaffective psychotic illness associated with viral CNS infections, as well as schizophrenia. There was no evidence of increased risk in relation to bacterial infections. When divided into specific agents, exposures to mumps virus or cytomegalovirus were associated with subsequent psychoses. CONCLUSIONS: Serious viral CNS infections during childhood appear to be associated with the later development of schizophrenia and nonaffective psychoses. The association with specific viruses suggests that the risk is related to infectious agents with a propensity to invade the brain parenchyma.

Decline in cognitive performance between ages 13 and 18 years and the risk for psychosis in adulthood: a Swedish longitudinal cohort study in males.

CONTEXT: Clear evidence from many prospective, population-based studies indicates that patients who develop psychosis in adulthood experienced various cognitive deficits during childhood and adolescence. However, it is unclear whether these deficits become more severe during adolescence. OBJECTIVE: To assess the influence of cognitive developmental trajectories in adolescence and young adulthood on the risk for psychosis in adulthood. DESIGN: Longitudinal cohort study. SETTING: Academic research. POPULATION-BASED COHORTS: Four population-based cohorts of adolescent boys and young men born in Sweden in 1953, 1967, 1972, and 1977, totaling 10,717 individuals, and followed up through December 31, 2006. EXPOSURE: Scores on tests of verbal, spatial, and inductive ability at age 13 years and in equivalent tests at army conscription (age 18 years). MAIN OUTCOME MEASURE: Hospital admissions for nonaffective or affective psychoses in adulthood. RESULTS: A relative decline (compared with the unaffected population) in verbal ability between ages 13 and 18 years was associated with increased risk for schizophrenia and for other nonaffective and affective psychoses (adjusted hazard ratio for schizophrenia for an increase of 1 SD in verbal ability, 0.59; 95% CI, 0.40-0.88; P = .009). Decline between ages 13 and 18 years was a much stronger predictor of psychosis than the verbal ability score at age 18 years alone. The association remained significant after adjustment for urbanicity, parental educational level, and family history of psychosis and persisted when cases with onset before age 25 years were excluded, indicating that this was not a prodromal effect. CONCLUSIONS: A relative decline in cognitive performance in adolescence and young adulthood, particularly in verbal ability, is associated with increased risk for psychosis in adulthood, and a relative decline in verbal ability between ages 13 and 18 years is a stronger predictor of psychosis than verbal ability at age 18 years alone. This suggests an impairment of late neurodevelopment affecting the acquisition of verbal skills in adolescent boys and young men who later develop psychosis.