Depression is a common and serious medical illness that causes feelings of sadness. It can lead to a variety of emotional and physical problems and can decrease your ability to function at work and at home. Symptoms of depression include fatigue, anxiety, irritability, restlessness, loss of enjoyment, appetite changes, changes in sleep patterns, and thoughts of suicide. Almost 7% of the population experiences at least one major depressive episode in their life. Itâ€™s more common in women thanÂ men.