Mood Disorders is the category for psychological disorders that manifest in mood altering symptoms. The most common mood disorders are Depression and Bipolar Disorder.
Bipolar Disorder is characterized by alternating periods of significant depression and mania or hypomania. During the manic phase, individuals may exhibit inflated self-esteem, decreased need for sleep, fast and nonstop talking, racing thoughts, increased involvement in pleasurable activities (i.e. sexual promiscuity, drug use, foolish money spending), and impulsiveness. During the depression phase, symptoms are similar to those experienced by an individual with depression without manic cycles.
Depression is a condition that involves symptoms of depressed mood and a lack of interest or ability to get satisfaction from normally pleasurable activities. Depression can also have a number of other effects, including: changes in sleep (increase or decrease), significant weight loss or gain, loss of energy, irritability, restlessness, difficulties in concentration and attention, and thoughts of suicide.