Decreased ability to take pleasure in things

It is very common for a depressed person to lose interest in things that were previously a source of pleasure and enjoyment such as hobbies, sports, and other interests such as reading, or watching movies. Enjoyment of sexual activity is often reduced. The person no longer feels any happiness or pleasure in life, and may withdraw from a variety of activities because they see little point in continuing to do them. The psychiatric term for this loss of pleasure is anhedonia.

Suicidal thoughts and behavior

A depressed person may become extremely sad, and is consumed with feelings of misery, hopelessness, and despair. These feelings may be so extreme as to make it feel as though life is not worth living. In fact, the effort of making it through one day to the next, or even from the morning to the afternoon, can seem to be almost an unbearable and impossible burden. With such an extremely negative mind-set, the person is usually unable to think clearly and rationally about the true state of his/her life.

People can begin to think that they deserve to feel miserable, and that they are being punished for some terrible thing they have done (but which is actually untrue). They cease to get any fun or enjoyment out of life and may not be able to see any likelihood of things improving. It is at this point that the very depressed person may see little point in continuing to struggle from day to day. The person feels that he/she is a burden to others, and may come to believe that it would be better for everyone if he/she was no longer around. It is in this negative frame of mind that thoughts of suicide - and suicidal acts - may occur.

Although such thoughts are common in depression, not everyone who is depressed feels suicidal. A depressed person may have occasional passing ideas that he/she would be better off dead but are able to overcome these, most of the time, by being aware of positive things in his/her life (such as a valued relationship, or loving dependant children) that are reasons for keeping going. Some severely depressed people, however, may think of suicide constantly, dwelling on the topic and planning in detail ways of killing themselves.

Anxiety

Depressed people often experience high levels of anxiety and this can occur even if they have never had problems with anxiety before. In fact, some degree of anxiety is found in up to 90% of depressed people.

Anxiety may be experienced as a persistent mood that lasts all day, not attached to any particular thought or situation (free-floating anxiety), or it may come and go as episodes of acute anxiety with panic attacks. In these attacks, the person experiences severe emotional and physical symptoms (such as sweating, shaking, upset stomach and shortness of breath), which reach a peak within 10 minutes. They may be repeated frequently in a 24 hour period. Going to work, attending social gatherings, doing the shopping or deciding what to wear may cause sufferers to become agitated, worried and distressed. This may become so bad that they avoid these situations altogether, possibly by spending the whole day in bed.

Decreased self-confidence

Depression is almost always associated with loss of self-esteem and self-confidence. The depressed person may no longer feel in control of his/her life and things that were accomplished easily before may now seem very difficult. Depressed people look at everything in a black, negative, and pessimistic light. They tend to be very self-critical and are unable to acknowledge that they can do anything well. They are unreasonably tough on themselves and see themselves as a failure.

If people have never experienced depression before, they may be unable to recognize that what is happening to them is actually an illness. They may blame themselves for the problems they are having and tell themselves they are not trying hard enough. Relatives and friends may do the same, adding further comments about "pulling socks" up. This sort of moralizing talk is far from helpful, and makes the depressed person feel even worse about himself/herself.

Impaired concentration and memory

Not only does depression make people think in a negative way; it also affects the efficiency of the thinking process. This might affect the ability to concentrate on things, especially for long periods, for example, when reading a book or watching a TV program. Depressed people often perform less well on tests of memory and concentration than people who are not depressed. In severe cases, they may even perform badly enough to appear to be demented. In general, the worse the depression, the worse are these problems with thinking. As the depression lifts, thinking becomes more efficient again. Depression does NOT cause dementia or brain damage.

Sleep problems and low energy levels

Problems with sleeping are commonly experienced by depressed people. Sleep is a complicated brain and body function. Broadly, it consists of two quite different states of sleep: Non-Rapid Eye Movement sleep (NREM) and Rapid Eye Movement sleep (REM). NREM sleep is divided into four stages depending on how deep the sleep is. REM sleep is the stage of sleep during which vivid dreaming occurs.

The normal pattern of sleep is disturbed in depressed people. The time taken to move between the stages of NREM sleep to REM sleep is altered and the amount of time spent in the different phases of the sleep cycle is also changed. In general NREM sleep is reduced and REM sleep increased. These may be experienced as difficulties getting to sleep (initial insomnia), waking up frequently during the night (middle insomnia), and waking early in the morning and being unable to get back to sleep (terminal insomnia). A less common sleep problem with depression is the need to sleep excessively (hypersomnia).

Depressed people generally experience low energy levels. They feel tired for much of the time and are easily fatigued.

Indecision

Someone who usually has no problems with making decisions can become significantly indecisive during a depressive illness. Choices that were previously easy and routinely made can seem incredibly complicated and difficult. A depressed person may not be able to decide what to wear or what to buy at the shops. This can be frustrating and cause the person to feel worse about himself/herself.

Decreased motivation

Loss of motivation is almost invariably present during an episode of depression. A depressed person may feel so negative and so low in spirits that it becomes difficult to even think of things to do. The person tends to expect failure or disappointment and, in addition to this, usually finds it difficult to be motivated due to extreme tiredness and exhaustrion.

Appetite and weight

The most common weight change seen in depressed people is weight loss that is not related to dieting, but caused by a loss of appetite. It may be very rapid and severe and can even be life-threatening. Less commonly, a depressed person will experience an increase in appetite (hyperphagia), often for sweet, rich foods, which may cause weight gain.

Somatic aches and pains

People with depression might feel physically unwell, and complain of generalized body aches, or may be more concerned about a more localized type of pain, e.g. headache, chest pain, or backache.

Depression can also cause a slowing of intestinal movements, which may be experienced as dyspepsia (pain in the stomach), fullness of the abdomen, and constipation. In elderly people, where intestinal action may be already sluggish, such further slowing during a depressive episode may lead to complete paralysis of the bowel (paralytic ileus).

All such symptoms can obviously be misinterpreted as signs of physical illness, however, more often than not, they are symptoms of the depressive illness itself.