Depression is a medical condition; it is also one of the most common and serious mental illnesses in the country. Feeling sad or a feeling of emptiness, loss of interest in activities (which were once a favorite), overeating or complete loss of appetite due to loss of interest in food, etc. are some of the starting indicators of depression.

This is normally followed by insomnia or irregular sleeping patterns for persistent periods, feeling zapped out of energy, and general laziness, which is the result of no interest in activities. These are the tell-tale signs and symptoms of a person going through depression.

As the severity of the condition grows, depression can also lead to suicidal thoughts which might be the result of a feeling of hopelessness. A person who is depressed will exhibit behavioral traits which include anxiety, irritability, and feeling guilty for no reason at all.

The types and causes of depression are varied since these can be due to any of the factors including genetics, biological, environmental, and certain psychological factors. Identifying the types and causes of depression will lead to a better understanding of the triggers.

For ease of reference, depression is classified into the following subtypes, with their causes explained.

Major depression: This can be classified as one of the more severe categories of depression, with causes that include triggers and symptoms like loss of interest, unexplained weight loss or gain, insomnia, restlessness and feeling agitated, trouble concentrating, and the ultimate thought of committing suicide. This is a type classified under clinical depression in which the sufferer exhibits one of the common causes and types of depression in their daily routine.

Persistent depressive disorder (PDD): This is a chronic condition which is persistent with symptoms that are similar to that of clinical depression. The main cause that leads to persistent depressive disorder is the change in serotonin levels in the brain. Serotonin is a chemical that controls emotions and impulse responses which help in making judgments, and also affects your perception. A chemical imbalance in these levels can trigger episodes of PDD.

Bipolar disorder: Also alternatively referred to as manic depression, this medical condition refers to extreme mood swings. Feeling too low or too happy, with phases of low and high energy levels are the primary symptoms of bipolar disorder. There are a number of biological differences and genetics that can be the major causes of a person suffering from bipolar disorder.

Seasonal Affective Disorder (SAD): This condition is mainly caused due to external factors like environmental changes, including changing seasons. SAD is one of the less common types and causes of depression.

Psychotic depression: One of the more severe types and causes of depression, which leads to psychotic breakdowns as the major symptom. Hallucinations, delusions, and paranoia are associated symptoms of a person suffering from psychotic depression.

Peripartum depression: Also alternatively known as postpartum depression, a condition which only women suffer from during and after the months of pregnancy and childbirth. This condition is not a common occurrence, and only women who are already in depression might phase into peripartum depression triggered due to a number of reasons.