Clinical or major depression - sometimes referred to as major depressive disorder or severe depressive disorder, is the most common mental disorder in the world. 

It affects 16% of the human population and is the leading cause of disability in America as well as in other countries. The World Health Organization expects that in 2020, clinical depression will become the second leading cause of disability in the whole world (next to heart disease).

Clinical depression is characterized by severe sadness and melancholy for a prolonged period of time. It can affect a man or woman's mental and behavioral attitude as well as his or her ability to carry out normal, everyday things.

So, what are the symptoms of clinical depression in adults?

1) Severe periods of sadness that could last for hours, days, and even weeks.

2) A decrease or loss in interest in the usual activities that he or she usually finds interesting

3) Appetite change (can be both loss and/or gain). The result is a ballooning up or down in weight.

4) Guilt over things that are relatively beyond their control such as getting sick.

5) A general feeling of worthlessness.

6) Lack of concentration on tasks and the inability to think logically including evidence of indecisiveness on things both significant and less so.

7) Exhaustion during physical activities including exercise, work, and even walking.

8) Irritability and a short temper

9) Periods of sobbing for seemingly no apparent reason.

10) Lack of self-confidence

11) Low self-esteem

12) Negative perception of the future or loss of hope over everything

13) Occasional feeling of anxiety.

14) Suicidal tendencies

15) Irregular sleeping patters that include hypersomnia or excessive sleeping, loss of rapid eye movement (REM) sleep, and insomnia or lack of sleep. This can be coupled with a difficulty in getting back to sleep. This in turn is naturally not good for a person's health or day to day existence.

What are the causes?

1) Medical conditions - Illnesses or traumatic experiences that are far too difficult to handle can cause depression. This might be cardiovascular disease, hypothyroidism, hepatitis, and major injuries.

2) Life experiences - Depression can be triggered by poverty, prolonged unemployment, career frustrations, multiple personal failures, gambling addiction, financial problems, loss of family members (spouse, child or relatives), a breakup within a committed relationship and other events that can trigger severe sadness.

3) Early life experiences - Childhood trauma like rejection or abandonment, chronic illness, neglect, death of loved one, sexual abuse, incest, psychological trauma, and other accidents that may not appear to be harmful during the early years but which can manifest later in life.

4) Psychological conditions - Lack of self-confidence and low self-esteem can trigger depression.

5) Physical conditions - Weight issues and physical deformities or disabilities can cause an adult to become depressed.

6) Living with a depressed person - Acquiring negative energy from someone who is depressed can increase the chances of depression. It's true - negative "vibes" can have a damaging effect!

7) Heredity - It is believed that there are depressive genes. If the parents have these kinds of genes, the offspring is likely to become depressed as well.

8) Postnatal depression or postpartum depression - mood changes after giving birth. This is often seen within 3 months after the delivery and would last for a number of months.

9) SAD or Seasonal affective disorder - Some people experience depression during winter when daytime is short. The Seasonal affective disorder can be countered with phototherapy.

It seems then that there are a number of causes for depression, the majority of which are not the sufferer's fault. This then reveals depression as the most cruel of illnesses. It's important for us to remember that only we, in the end, can control what goes on inside our minds. That is our last defense against this condition.