According to the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV; American Psychiatric Association, 2000) criteria, a diagnosis of Major Depression (MDD) requires a total of five symptoms, at least one of which is depression and/or anhedonia, and another four (three if both depression and anhedonia are present) symptoms from the following: appetite or weight disturbance (decrease or increase in appetite, weight, or both, or failure to make expected gains), sleep disturbance (insomnia or hypersomnia), psychomotor disturbance (agitation or retardation), fatigue or loss of energy, feelings of worthlessness or excessive or inappropriate guilt, concentration difficulties or indecisiveness, and suicidality (thoughts or behavior). Irritability is a mood equivalent for children and adolescents and may therefore be used instead of depressed mood. Depressed/irritable mood and (most of the) other symptoms need to be present most of the day, almost every day for at least 2 weeks and anhedonia (if present) should be marked. The syndrome requires presence of clinically significant distress, impaired functioning, or both. The disorder may have an acute or insidious onset, may be single or recurrent, melancholic or atypical, psychotic or nonpsychotic, and transitory or chronic.