Tell Me More About Depression.
6. What causes depression?
There is no single cause of depression and the term "major depressive disorder" likely describes several different types.
There is clear evidence that brain changes accompany depressive symptoms. MRI images have shown regions of the brain that are altered in size or function in depressed individuals. Specifically, depression is associated with large ventricles (areas for brain fluid) and reductions in the size of the frontal regions of the brain. Techniques to assess the brain at work, using MRI and PET scans also show those regions working differently in depressed individuals. Researchers have proposed that various nerve pathways are disrupted in different brain areas.
There are many factors that create a vulnerability to depression, including personal early loss, life difficulty, substance abuse, medical illness, and gender. These factors disrupt neurotransmitters in the brain (serotonin, dopamine and norepinephrine are the most studied), causing alterations in nerve pathways that are responsible for regulation of mood, sleep, attention, appetite, energy and other symptoms involved in depressive disorders.
References:
Kendler KS, Thornton LM, Gardner CO. Genetic risk, number of previous depressive episodes, and stressful life events in predicting onset of major depression. Am J Psychiatry 2001;158:582-586.
McEwen BS. Mood disorders and allostatic load. Biol Psychiatry 2003;54:200-207.
Nemeroff CB. Recent advances in the neurobiology of depression. Psychopharmacol Bull 2002;36 Suppl 2:6-23.
6a. Can medical conditions or medication cause depression?
Disorders frequently associated with depression.
| Disorders |
Examples |
| Neurological |
Alzheimer’s disease, Parkinson’s disease |
| Systemic |
Viral and bacterial infections |
| Inflammatory |
Rheumatoid arthritis, Lupus erythematosis |
| Endocrine |
Thyroid disorders, Vitamin deficiencies |
| Other |
AIDS, Cancer, Cardiopulmonary disease |
Although there are reports of depression being induced by virtually every medication, it is often difficult to establish cause and effect. However, certain types of medicines, including anti-hypertensive and anti-arrhythmic cardiac drugs, cancer drugs, steroids and some anti-bacterial agents, have been frequently associated with depression. A more extensive list is provided below.
Figure 3: Medications frequently associated with depression.
| Medications |
Examples |
| Anti-bacterials and anti-fungal agents |
Ampicillin, Clotrimazole, Tetracycline |
| Cancer drugs |
Beiomycin, Mithramycin, Zidovudine |
| Cardiac and anti-hypertensive drugs |
Beta blockers, Clonidine, Digitalis |
| Steroids and hormones |
Corticosteroids, Oral contraceptives |
| Analgesics and anti-inflammatory agents |
Ibuprofen, Opiates, Phenacetin |
| Stimulants and appetite suppressants |
Diethylpropion, Fenfluramine, Phenmetrazine |
| Sedatives and hypnotics |
Barbiturates, Benzodiazepines, Chloral hydrate |
| Neurological agents |
Amatadine, Baclofen, Levodopa |
| Miscellaneous drugs |
Disulfiram, Isotretinoin, Metaclopramide |
Reference:
Enns MW, Swenson JR, McIntyre RS, et al. Clinical guidelines for the treatment of depressive disorders: VII Comorbidity. Can J Psychiatry 2001;46 Suppl 1:77S-90S. |
