Depression is a psychological disease; but sometimes it could be due to physical causes. So we will highlight the most important physical causes that could lead to depression.

1. Hyperthyroidism: medical studies showed that there is close relation between increased production of thyroxin hormone due to hyperthyroidism and the incidence of depression.
2. Oral contraceptive pills: These pills consist mainly of estrogen and progesterone, which could increase body levels of serotonin leading to depression.
3. Vegetarian diet: this diet means not eating fish which is the main source of fatty acids. Recent medical studies showed that fatty acids are very important for improving mood and avoiding depression.
4. Overconsumption of sugars or carbohydrates: this eating style leads to increased levels of glucose and decreased dopamine, leading to depression.
5. Overconsumption of caffeine as tea and coffee especially in night: excessive caffeine causes insomnia and sleeping disorders as well as stress and sometimes depression.
6. Medications: depression could be a significant side effect of administration of certain drugs such as antihypertensive drugs containing propranolol as well as interferon (for treatment of hepatitis C).
7. Smoking: cigarettes contain nicotine which decreases the level of dopamine, leading to depression.