Neurotransmitter changes - monoamine hypothesis
Research evidence is clear that there are Reduced levels of Serotonin and Noradrenalin monoamine activity in the brains & CSF of depressed people.
Current hypotheses suggest that this is due to a combination of:
- increased MAO-A Levels within neurons, as well as
- increased Monoamine transporter concentrations At synaptic terminals. The overall effect is that monoamines are rapidly removed From synaptic clefts and returned intracellularly, where increased levels of MAO-A degrade them
Evidence to support these theories is found in functional brain scanning. For example, the SPECT scans below show increased dopamine transporter Concentration in the basal ganglia of a depressed (L) vs. healthy (R) brain
Source: Brunswick et al. Greater availability of Dopamine transporters. AJP 2003