Depressive Disorder: Causes

The exact cause of the depressive disorder is unknown. Heredity plays an unclear role; Depression is more common among relatives of a patient with a depression of the 1st degree of kinship, a high concordance between monozygotic twins. Hereditary genetic polymorphism of the activity of the carrier of serotonin in the brain can be triggered by stress. People who have experienced violence in childhood or other severe stresses and have a short allele of this vector are twice as likely to develop depression as compared to those with a long allele.

Other theories focus on changes in neurotransmitter levels, including disturbances in the regulation of cholinergic, catecholaminergic (noradrenalinergic and dopaminergic), serotonergic (5-hydroxytryptamine) neurotransmission. Neuroendocrine dysregulation can also be important with a special emphasis on the three axes: hypothalamic-pituitary-adrenal, hypothalamic-pituitary-thyroid and growth hormone.

Psychosocial factors also appear to be involved. Significant life stressors, especially separation and loss, often precede episodes of major depression; However, these events usually do not cause a prolonged, severe depression, except for people with a predisposition to mood disorders.

Patients who had a history of major depression in the past have a significant risk of subsequent episodes. Introverted people, as well as those who have anxious personality traits, are more likely to develop a depressive disorder. Such people often have a lack of social skills in adapting to problem life situations. Depression can also develop in people with other mental disorders.

In women, the risk of developing depression is higher, but there is no explanation for this theory. Perhaps this is due to a greater susceptibility or increased reaction to daily stress, an elevated level of monoamine oxidase (an enzyme that breaks down neurotransmitters that are important in maintaining the mood) and endocrine changes associated with the menstrual cycle and menopause. With postpartum depression, symptoms develop for 4 weeks after childbirth; probably, endocrine changes are involved, but the specific cause is unknown. In addition, women are more likely to have thyroid dysfunction.

With seasonal affective disorder, symptoms develop with seasonal frequency, usually in autumn and winter. This disorder tends to manifest itself in those climatic zones where long and severe winters. Depressive symptoms or disorders can occur with various physical illnesses, including thyroid and adrenal diseases, benign and malignant brain tumors, stroke, AIDS, Parkinson's disease, multiple sclerosis. Certain drugs, such as glucocorticoids, some beta-blockers, antipsychotics (especially in the elderly), reserpine, can lead to the development of depressive disorders. Abuse of some substances taken for entertainment (for example, alcohol, amphetamines), can lead to the development of concomitant depression. Toxic effects or the withdrawal of these drugs can cause transient depressive symptoms.

Some Causes of Symptoms of Depression and Mania

Type of Disorder	Depression	Mania
Connective tissue	Systemic lupus erythematosus	Rheumatic fever Systemic lupus erythematosus
Endocrine	Addison's disease Cushing's Disease Diabetes Hyperparathyroidism Hyperthyroidism and hypothyroidism Hypopituitarism	Hyperthyroidism
Infectious	AIDS Progressive paralysis (parenchymatous neurosyphilis) Flu Infectious mononucleosis Tuberculosis Viral hepatitis Viral pneumonia	AIDS Progressive paralysis Flu Encephalitis of St. Louis
Neoplastic	Cancer of the head of the pancreas Disseminated carcinomatosis
Neurological	Tumors of the brain Severe epileptic seizures (temporal lobe) Craniocerebral injury Multiple sclerosis Parkinson's disease Apnea in a dream Stroke (frontal area to the left)	Severe epileptic seizures (temporal lobe) Diencephalic tumors Craniocerebral injury Huntington's disease Multiple sclerosis Stroke
Disturbances in nutrition	Pellagra Pernicious anemia
Other	CHD Fibromyalgia Renal or hepatic impairment
Mental	Alcoholism and other disorders associated with the use of psychoactive substances Antisocial personality Demential disorders in an early stage Schizophrenic disorders
Pharmacological	Abolition of amphetamines Amphotericin B Anticholinesterase insecticides Barbiturates Cimetidine Glucocorticoids Cycloserine Indomethacin Mercury Metoclopramide Phenothiazines Reserpine Thallium Vinblastine Vincristine	Amphetamines Some antidepressants Bromocriptine Cocaine Glucocorticoids Levadopa Methylphenidate Sympathomimetic drugs

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