Mood disorders have a wide range of presentation – from major depressive episodes to mania. Both depression and mania can present with irritability; the notable differences between them are discussed in this chapter. Persistent sad mood and lack of enjoyment in usual activities is typically noted in depression, while a lack of need for sleep along with euphoric mood is typical for mania. Due to the spectrum of intervening mood disorders such as bipolar II illness and persistent depressive disorder, a thorough psychiatric evaluation is important. Since mood disorders may lead to dangerousness in the form of self-harm behavior, suicidality, and violence, a sudden and persistent change in mood should be considered a psychiatric emergency. Suicide is rare but unpredictable. Direct questions on whether a patient has thoughts about self-harm are important to differentiate habitual threatening statements from real intent. Treatment options for mood disorders including psychotherapy and medication management are discussed. Episodic mood disorders covered in this chapter are all treatable conditions when identified promptly and under the care of experienced mental health providers.