Final answer:
Increased serotonin levels are NOT a brain function change associated with severe depression. In fact, depression is typically linked to low serotonin levels, and antidepressants aim to increase these levels.
Step-by-step explanation:
The option that is NOT a change in brain function associated with severe depression is: A. Increased serotonin levels. Changes commonly associated with severe depression include reduced hippocampal volume, dysregulation of the hypothalamic-pituitary-adrenal axis, and impaired neuroplasticity. Typically, serotonin levels are low in individuals with depression, and antidepressants often work by increasing these levels to normal. In contrast, increased serotonin levels are not characteristic of severe depression.
Evidence supports that there is a relationship between stress, brain function changes, and depression. Chronic stress and depression are linked to several changes in the brain, such as dysregulation of the hypothalamic-pituitary-adrenal axis, alterations in neurotransmitter systems like serotonin and noradrenaline, and changes in brain structure and function. These alterations can manifest as reduced volume in the hippocampus, which is important for memory and emotional responses, and impaired neuroplasticity, affecting the brain's ability to adapt and form new connections. Moreover, dysregulation of the immune system with increased levels of pro-inflammatory cytokines has also been observed in individuals with major depressive disorder (MDD).