Substance use disorders and psychotic disorders in epilepsy: a population-based registry study.

BACKGROUND: Epilepsy affects around 70 million people worldwide. Psychiatric comorbidity may add to the burden of the disease. We studied substance use disorders and psychotic disorders among people with epilepsy from a population-based perspective. METHODS: Norwegian specialist health services (hospitals and outpatient clinics) report diagnoses for individual patients to the Norwegian Patient Register. We used information on subjects born in 1930-1994 who were registered with a diagnosis of epilepsy at least once during the five-year period of 2008-2012. We compared the proportion of people with epilepsy registered with substance use disorders (alcohol use disorders or non-alcohol drug use disorders) and psychotic disorders (schizophrenia spectrum disorders or bipolar disorder) with similar figures in the population without epilepsy. We applied chi-square tests and log-binomial regression for analysis. RESULTS: Overall, 0.90% of the Norwegian adult population was registered with epilepsy in somatic hospitals during 2008-2012. The total proportion registered with alcohol use disorder was 5.74% among people with epilepsy and 1.29% in the population without epilepsy (age- and sex-adjusted relative risk [RR]: 4.42, 95% confidence interval [CI]: 4.22-4.62). The corresponding figures were 4.32% and 1.22% (RR 3.86 [95% CI: 3.67-4.06] for drug use disorder, 1.72% and 0.60% (RR 2.94 [95% CI: 2.71-3.19]) for schizophrenia spectrum disorders, and 1.50% and 0.68% (RR 2.29 [95% CI: 2.10-2.49]) for bipolar disorder. CONCLUSION: People with epilepsy were more often registered with substance use disorders and psychotic disorders than people without epilepsy. Psychiatric comorbidity requires particular attention in both diagnostic work-up and management of epilepsy, and creates complex medical challenges that require close cooperation between neurologists and psychiatrists. These findings may have implications for the organization and further development of comprehensive epilepsy care.