There are many kinds of depression. Melancholic depression is a type of clinical depression wherein one is unable to feel pleasure. On top of this, one also suffers from decreased appetite, insomnia, and physical agitation. Another type of depression, which is cyclical in nature, is atypical depression. When one has atypical depression, one is able to sleep, eat, and feel pleasure like regular people do. However, these activities are always coupled with a feeling of lethargy. Meanwhile, psychotic depression refers to a type of clinical depression that manifests itself through delusional or even psychotic perceptions. Experts believe depression is largely affected by estrogen production or the lack thereof. This section contains articles that are all about depression.