Bipolar disorder and gambling disorder comorbidity: current evidence and implications for pharmacological treatment.

Background: The co-occurrence of bipolar disorder (BD) and gambling disorder (GD), though of clinical and public health importance, is still scarcely investigated. Comorbid BD-GD subjects experience a more severe course of illness and poorer treatment outcome, due to a range of clinical and psychosocial factors that collectively impede remission and recovery. The aim of our paper is to review the role of pharmacotherapy in the treatment of comorbid BD-GD, in order to support clinical decisions according to the best available evidence.

Methods: A qualitative systematic review of studies on pharmacological treatment in comorbid BD-GD was performed. A comprehensive literature search of online databases, bibliographies of published articles and gray literature was conducted. Data on efficacy, safety and tolerability were extracted and levels of evidence were assessed. We also provide a brief overview of current epidemiological, neurobiological and clinical findings, with the intention of proposing a dimensional approach to the choice of available drugs.

Results: The only drug with a high level of evidence is lithium. Considering the inclusion of GD in DSM-5 'Substance-related and Addictive Disorders' category, we discuss the use of other drugs with a high level of evidence currently used in BD subjects with co-occurring substance use disorders.

Limitations: Only few clinical trials are available and the population is limited; therefore no conclusive evidence can be inferred.

Conclusions: Further randomized controlled trials are required to evaluate the efficacy of pharmacological treatment strategies in large samples of patients with comorbid BD-GD. Also, attempts should be made to identify other shared clinical and psychopathological domains that are amenable to treatment.