Changes in appetite are a symptom of many medical and psychiatric disorders.
When a person’s appetite is either more or less than normal for several days or weeks, or when the appetite changes result in an unintentional loss or gain of more than 5 percent of body weight, there may be an underlying medical or psychiatric condition.
Different forms of depression can lead to changes in appetite and weight. For example, melancholic depression is often associated with a loss of appetite, while atypical depression often leads to increased appetite.
Although it’s not a mental illness, bereavement shares many characteristics with depression and can lead to increased or decreased appetite and weight.
Other conditions that can result in loss of appetite are mania, hypomania, and bipolar and schizoaffective disorders.