This chapter identifies environmental causes as well as biological triggers for psychiatric symptoms in people with epilepsy. It stresses that these symptoms should receive medical attention, and discusses some of the safe and effective treatments that are available. The chapter focuses on interictal depression, other interictal psychiatric disorders, and ictal and peri-ictal psychiatric disturbances. Interictal depression and other interictal psychiatric disorders include adjustment disorders, major depression, dysthymic disorder, bipolar disorder, atypical depressive syndromes, medication-induced mood disorders, anxiety disorders, and psychotic disorders. The development of psychiatric symptoms in people with epilepsy appears to be associated with a number of biological, psychological, and social factors. Psychiatric symptoms caused by antiepileptic drugs (AEDs) are treated by lowering the medication dose or changing to a different AED. Mood stabilizers are used to treat bipolar disorder and conditions with mood instability. With proper treatment, psychiatric disturbances can substantially improve or even completely resolve.