Fidgure 5. (drugabuse.gov, 2017)
In a normal brain, the brain cells communicate with each other using chemicals, called neurotransmitters. These signals can cause emotions, can cause physical movement, and they help us perceive what is going on around us. In a person who is not affected by depression, there are enough neurotransmitters to ensure a stable mood and emotional state. Specifically, serotonin, dopamine and norepinephrine are able to be synthesized, released and degraded in the proper amounts. Someone who does not suffer from mood disorder has a mood that is stable over an extended period of time. Depression is described further here:
Depression is a heterogeneous disease process that mainly stems from neurotransmitter abnormalities. But, pathology may be more strongly influenced by genetics than previously thought, up to 40%. Environmental effects are accountable for the remaining susceptibility (Hasler,2010). These adverse effects are most influential when they occur in childhood, and when they are prolonged stressors such as being out of a job for months.
Depression is considered a stress disorder, but suprisingly most patients do not have HPA axis abnormalities.
Monoamines are neurotransmitters involved in regulation of mood, attention, reward processing, sleep, appetite, and cognition (Hasler, 2010). A deficiency in monoamine neurotransmitters is the main suspected pathophysiologic cause of MDD. In drug trials, monoamine reuptake inhibitors have been shown to improve depression in individuals. Thus the link between these neurotransmitters, including serotonin, and the cause of depression is strong.
Diagnostic criteria must include at least 5 of 9 features, but must include either #1 or #2, for two or more consecutive weeks.
*1. Depressed mood or irritable
*2. Decreased interest or pleasure in activities
3. Significant weight change (5%) or change in appetite
4. Change in sleep
5. Change in activity level of the brain; retardation or agitation
6. Fatigue
7. Feelings of guilt or worthlessness
8. Difficulty concentrating
9. Suicidal Ideation
