Clinical depression is a serious type of depression that is characterized by loss of interest and pleasure in activities and a consistently depressed state that lasts at least two weeks, according to Mayo Clinic. Clinical depression interferes with aspects of daily living, such as work and relationships.
Symptoms of clinical depression, also known as major depression, include fatigue, feelings of worthlessness, a 5 percent increase or decrease of weight in a month, suicidal thoughts and lower than usual concentration, states WebMD. Other symptoms include too much or too little sleep and restlessness. Clinical depression is commonly treated with either antidepressants, talk therapy, psychotherapy or a combination of all three.