The aetiological factors behind comorbid obsessive-compulsive disorder and generalized anxiety disorder

Abstract

Individuals with obsessive-compulsive disorder (OCD) often experience comorbid anxiety disorders, especially generalized anxiety disorder (GAD). Comorbid OCD and GAD is associated with increased symptom severity, more suicidal acts, increased duration of illness, and other undesired outcomes compared with OCD-only patients. Despite the shared underlying features of these two disorders, their high level of comorbidity, and the worrying outcomes of the comorbid form, the aetiology behind comorbid OCD and GAD remains mostly unknown.

The aim of this systematic review is to shed light on the aetiological factors behind comorbid OCD and GAD. Systematic search was conducted in the following databases: ProQuest, Scopus, and all EBSCOhost Databases. 11 peer-reviewed articles were included in the review.

Three main categories of aetiological factors were identified. First, familiality and shared genetic liability play an unquestionable role. The exact genetic mechanisms require further research as the only identified factor in this review was lower plasma levels in the brain-derived neurotrophic factor (BDNF). Second, onset of GAD may be a consequence of prior OCD. New questions about this timely order were also raised as one study found GAD symptoms to precede the onset of diagnosable OCD. Third, OCD and GAD share thought processes and emotions. High levels of worry, (anger) rumination, intolerance of uncertainty, and fear during the symptoms were identified. Trait anxiety also connected the two disorders.

The results of this review come mainly from studies on wider OCD comorbidity. Thus, phenomena such as higher BDNF serum levels or shared thought processes and symptoms might be common across various disorders and their combinations. The need for new studies focusing solely on the comorbid OCD and GAD is apparent. Early treatment of OCD or GAD will likely decrease the chances of comorbid diagnoses. This comorbid phenotype may also carry a higher risk for treatment discontinuation, especially when it comes to pharmacological treatment.