Biochemical Abnormalities in Unipolar Mood Disorders
Psychologists have explored several causal factors of unipolar mood disorders. They have found out that unipolar mood disorders are partly influenced by certain biochemical abnormalities in the body. These biochemical abnormalities can be found inside the brain (through the neurotransmitters of the monoamine class - norepinephrine, dopamine and serotonin) and the hormones (particularly the cortisol adrenocorticotrophic hormone or ACTH, and thyroid levels).
The monoamine hypothesis, which states that the lower levels of neurotransmitters norepinephrine, dopamine, and serotonin in the brain are partly responsible for depression, however, is not completely justified in research. For example, people diagnosed of major depressive disorder with melancholic features showed higher levels of norepinephrine; only a minority of depressed suicidal patients have lowered serotonin activity; and, the effects of antidepressants are only felt 2 to 4 weeks after administration, that is, when the levels of neurotransmitters in the brain have already normalized. The monoamine hypothesis, therefore, is not a valid explanation for depression; but it remains a known fact that depressed individuals show markedly altered neurotransmitter levels of the monoamine class. Consequently, psychologists have refocused their attention on mapping the complex interaction of these neurotransmitters in relation to depression.
Two important endocrine systems that respond to stress and emotions are the hypothalamic-pituitary-adrenal (HPA) axis and the hypothalamic-pituitary-thyroid (HPT) axis. These axes release hormones that regulate the body's response. Studies show that around 20 to 40 percent of mildly depressed patients and around 60 to 80 percent of patients with major depressive disorder show high levels of cortisol (ACTH) in the body. However, the levels of cortisol in the body do not seem to dissipate as would be expected. It appears that the feedback loop - the one that tells the body to stop producing cortisol - is malfunctioning. A chemical called dexamethasone can suppress the production of cortisol in normal individuals, but is not capable of doing so with depressed individuals. Thyroid levels also affects our mood. For example, depressed people also report of having low thyroid levels.
Frequently Asked Questions
- What characterizes abnormalities in the biochemical system of people diagnosed with bipolar disorder?
- How about in people with panic disorder? How are theirs different from those with bipolar disorder?
- How about in unipolar mood disorders? Do these abnormalities present themselves in different ways? Or, do they follow a specific pathway similar in all three mental disorders?