The symptoms of depression may vary widely between individuals. However, one of the classic symptoms of depression is a long-term, persistent feeling of sadness. Some of the symptoms of clinical depression include:

• Feelings of sadness, hopelessness and tearfulness that may last for weeks or months. This feeling of sadness does not pass as might sadness felt in response to a life changing or tragic event and the sadness can become severe, even giving rise to symptoms of psychosis.
• Irritability and intolerance of others, perhaps leading to fights with other people.
• Excessive feelings of guilt.
• Difficulty in making decisions.
• Apathy and loss of interest in activities that used to be enjoyable. While mild depression can lead to a loss of interest in hobbies and sometimes work, more serious depression can lead to a loss of interest in simple, routine daily activities such as eating, sleeping, maintaining personal hygiene and maintaining social relationships.
• Symptoms of anxiety and even phobias and panic attacks may coexist with the depression.
• Unexplained tiredness and feelings of stress and being overwhelmed.
• Sleep disorder that may manifest as either oversleeping or as insomnia or difficulty in falling or staying asleep.
• Changes in eating habits that manifest either as a loss of appetite or as excessive eating with bouts of binging. These eating habits may lead to serious malnutrition or obesity as well as symptoms such as constipation, diarrhea and irritable bowel syndrome.
• Loss of sex drive or libido.
• Deterioration of personal and social relationships.
• Feeling vague pains and aches.
• Alterations in the menstrual cycle in women with depression.
• Thinking about and planning suicide. In major depressive disorder, patients may start thinking about killing themselves to end the misery.