Moderate caffeine intake (less than 6 cups/day) has been associated with less depressive symptoms, fewer cognitive failures, and lower risk of suicide. Conversely, in rare cases high doses of caffeine can induce psychotic and manic symptoms, and more commonly, anxiety. Patients with panic disorder and performance social anxiety disorder seem to be particularly sensitive to caffeine, whereas preliminary data suggests that it may be effective for some patients with obsessive compulsive disorder (OCD).
The anxiety effect of caffeine is influenced by a polymorphism of the A2A receptor. In summary, caffeine can be regarded as a pharmacological tool to increase energy and effortful behavior in daily activities. More studies are necessary to establish the role of caffeine intake in psychiatric disorders, especially its putative efficacy on depressive mood and cognitive/attentional disorders.1