The various types of depression have different causes as well as different levels of severity. which of the following best describes clinical depression?
a feeling of overwhelming sadness that usually follows a traumatic event
a medical condition that may occur due to a chemical imbalance in the brain
alternate feelings of extreme happiness and extreme sadness

Symptoms of clinical depression

A significant change in the personality and the persistent state of sadness and despair are the main signs of clinical depression. Other symptoms are manifested in an irritable mood, feelings of incompetence or excessive guilt, loss of interest in previously enjoyed activities, changes in appetite and sexual desires.

sleep disorders (insomnia or hypersomnia), reduced concentration, loss of energy, recurrent thoughts about death and suicidal thoughts complement the clinical picture of clinical depression.

Because without physical activity, the body has extra "energy" if you will, and so when it is time for bed you are not tired, so you end up staying up all night. also there is probably an effect on your internal clock, which messes with your melatonin production which goes hand in hand with your sleep cycle