The severity of psychotic symptoms in patients with bipolar affective disorder (BPAD) correlated inversely with response to lithium therapy, according to a study published in JAMA Psychiatry . Other findings suggested that the antigen presentation pathway and inflammatory cytokines such as tumor necrosis factor (TNF), interleukin-4 (IL-4), and interferon gamma (IFNγ) may play a biological role in lithium treatment response in BPAD. BPAD and schizophrenia can be difficult to distinguish clinically during episodes of acute illness because of overlapping psychotic symptoms. In addition, these two disorders have a 68% shared genetic variation — the highest among all pairs of psychiatric disorders. However, while lithium is not effective in schizophrenia and may result in lithium-induced neurotoxic effects in patients with the disorder, ≥70% of patients with BPAD respond to lithium. These observations prompted the current study. Bernhard T. Baune, PhD, MD, MPH, disci...