40-60% of patients with obsessive compulsive disorder (OCD) do not respond adequately to serotonin reuptake inhibitors (SRIs). It is important to identify predictors of response to help individualize treatment and identify refractory patients early in the course of treatment.
We review the current literature on predictors of response to SRIs in adult patients with OCD including clinical features, neuropsychological profile, neuroimaging, genetics and other biological factors. We conducted a literature search in PUBMED database using the MeSH terms "Obsessive-Compulsive Disorder", "drug therapy", "treatment outcome", "neuroimaging", "genetics" "cytokines" and obtained 60 articles. Expert commentary: Poor-insight into obsessions, symmetry/hoarding and contamination/washing dimension and the presence of certain personality disorders are associated with poor response to SRIs. Orbitofrontal cortex, anterior cingulate cortex, caudate, putamen and thalamus volume changes in structural imaging studies and altered activity in the same regions in functional imaging studies were found predictive of poor response. However, there is inconsistency with regards to direction of change. Genes involving serotonergic and glutamatergic signalling pathways have emerged as predictors in recent studies. Studies with large sample size, standardised methodology and rigorous statistical analyses are required before predictors can be utilised in routine clinical practice.