General description
A depressive disorder is an illness that involves the body, mood, and thoughts. It affects the way a person sleeps, the way one feels about oneself, and the way one views the world around them. In contrast to the normal emotional experiences of sadness, loss, or passing mood states, clinical depression is a serious, persistent medical illness, which can interfere significantly with an individual's ability to function. Symptoms of depression include melancholy, loss of interest or pleasure in activities that were previously enjoyed, change in appetite or weight, oversleeping or difficulty sleeping, physical slowing or agitation, energy loss, feelings of worthlessness or inappropriate guilt, difficulty thinking or concentrating, and recurrent thoughts of death or suicide.¹ Without treatment, symptoms can last for weeks, months, or years. Appropriate treatment, however, can help most people who suffer from depression.

As is the case with many other diseases (such as heart disease), depressive disorders come in different forms. Major depression (also called unipolar depression) is manifested by a combination of symptoms (listed above) that interfere with the ability to work, sleep, eat, and enjoy pleasurable activities. Such disabling episodes may occur only once, but more commonly occur several times in a lifetime. A less severe type of depression, dysthymia, involves long-term, chronic symptoms that are not severely disabling, but keep one from feeling good or functioning well. Many people with dysthymia also experience episodes of major depression at some time in their lives.¹

Another type of depression is bipolar disorder, also called manic-depressive illness. Bipolar disorder is characterized by cycling mood changes of severe highs (mania) and lows (depression). These mood changes are most often gradual, but they may be dramatic and rapid. When in the depressed cycle, the individual may have any or all of the symptoms of a depressive disorder. When in the manic cycle, the individual may be overactive, overtalkative, and have a great deal of energy. Mania often affects thinking, judgement, and social behavior, causing serious problems. If left untreated, mania may worsen into a psychotic state.¹

Contributing factors
Modern brain imaging technologies have revealed that, in depression, neural circuits responsible for moods, thinking, sleep, appetite, and behavior fail to function properly, and the regulation of critical neurotransmitters (such as serotonin and norepinepherine) is impaired. The cause of these abnormalities is still unknown. Genetic research indicates that vulnerability to depression results from a combination of hereditary and environmental factors. Researchers now believe that the expression of psychological disorders such as depression is influenced by several genes, rather than a single defective gene.² Identification of these genes, each of which contributes only a small effect, has proven difficult.

Psychosocial and environmental stressors are known risk factors for depression. The hormonal system that regulates the body's response to stress is overactive in many patients with depression, and researchers are investigating whether this contributes to the development of the illness. Research has shown that stress in the form of loss, especially the death of close friends or family members, can trigger depressive episodes in vulnerable individuals.² Other research indicates that stressors such as social isolation or early-life deprivation can cause permanent changes in brain function that increase susceptibility to depression.²

Depression often occurs in conjunction with other physical and psychological conditions. After giving birth to a child, many women experience a period of depression known as post-partum depression. Women who suffer from premenstrual syndrome (PMS) often have symptoms of depression, as do people with post-traumatic stress disorder, alcoholics, and other substance abusers. Depression is also common in people suffering from life-threatening diseases like cancer or AIDS.

Conventional treatments
The most commonly used treatments for depression are antidepressant medication, psychotherapy, or a combination of the two. The treatment prescribed for an individual case depends on the nature and severity of the depression. Antidepressant medications take several weeks to be clinically effective even though they begin to alter brain chemistry with the first dose. These drugs influence the functioning of certain neurotransmitters, primarily serotonin and norepinephrine, known as monoamines. Older medications (tricyclic antidepressants and monoamine oxidase inhibitors) affect the activity of both of these neurotransmitters simultaneously. The disadvantage of these drugs is that they can be difficult to tolerate due to side effects or dietary restrictions. Newer medications, such as selective serotonin reuptake inhibitors (SSRIs), have a narrower range of activity and are associated with fewer side effects. While both generations of drugs have proven effective in treating depression, some people will respond to one type of drug but not another. Many clinicians find that combinations of different drugs work most effectively for treating depression, either by enhancing the therapeutic action or by reducing side effects. Patients with bipolar disorder are commonly prescribed antidepressants in combination with mood stabilizers (such as lithium or valproate) to control mania.

In mild to moderate depression, psychotherapy may be a treatment option. Research has shown that two types of psychotherapy, cognitive-behavioral therapy (CBT) and interpersonal therapy (IPT), can be effective for relieving depression. CBT helps patients change negative thought and behavior patterns associated with depression. IPT focuses on working through disturbed personal relationships that may contribute to depression. Studies indicate that while psychotherapy alone is rarely sufficient to treat moderate to severe depression, it may provide additional relief in combination with antidepressant medication. ²

Nutritional/lifestyle considerations
Several lifestyle factors can influence the frequency and severity of depressive episodes. It's important that depressed individuals spend time with other people and confide in someone rather than isolate themselves. Participation in social activities, hobbies, sports, religious, or cultural activities can help shift focus away from negative thoughts and emotions. Regular exercise can be helpful, as can stress-relieving techniques such as yoga, meditation, and prayer. People at risk for depression should avoid stimulants such as caffeine and nicotine as well as mood-altering substances such as alchohol and narcotics.

Nutrition can also play a role in depressive disorders, and a number of dietary supplements are promoted as natural mood-enhancers. The B-complex vitamins are involved in the production of many neurotransmitters needed for mental health, and deficiencies can upset emotional balance. Studies indicate that supplementing with monoamine precursors such as 5-HTP,^3-6 phenylalanine,^7-10 and tyrosine¹¹ can improve depressive symptoms in some people. Other nutrients involved in serotonin function, such as SAMe^12-17 and phosphatidylserine,^18,19 have also been shown to improve symptoms in some depressed individuals. The herb St. John's wort is commonly prescribed in Germany for treatment of depression,²⁰ and studies have shown its effectiveness to be superior to placebo and comparable to some prescription antidepressants.²¹ Because many of these dietary supplements may interact with prescription medications, they should only be used under a doctor's supervision.