Neurobiological studies suggest that primary neurotransmitter(s) involved in major depressive disorders is (are) a. dopamine b. serotonin c. glutamate d. norepinephrine e. dopamine and serotonin f. serotonin and norepinephrine

Major depressive disorders are a group of mental health disorders that are characterized by persistent feelings of sadness, hopelessness, and a lack of interest or pleasure in activities. These disorders can have significant impacts on an individual's daily functioning and overall quality of life.

In this step, let's briefly discuss the roles of the neurotransmitters listed in the answer choices. a. Dopamine: It is associated with reward, motivation, and pleasure systems in the brain. Imbalances in dopamine levels can lead to mood disorders, including depression. b. Serotonin: It is responsible for maintaining mood balance and regulating various body functions, such as appetite, sleep, and cognitive functions. Low levels of serotonin are often linked to depression. c. Glutamate: It is the primary excitatory neurotransmitter in the central nervous system. It is involved in memory, learning, and various cognitive functions. Glutamate is not specifically linked to depression, but disruptions in glutamate signaling have been implicated in several neuropsychiatric disorders. d. Norepinephrine: It is involved in regulating attention, alertness, and mood. Imbalances in norepinephrine levels are often linked to mood disorders, including depression. e. Dopamine and Serotonin: These two neurotransmitters are both involved in mood regulation, and their imbalances can contribute to depressive symptoms. f. Serotonin and Norepinephrine: These two neurotransmitters play essential roles in mood balance and regulation, and their imbalances can contribute to depressive disorders.

Based on the roles of the neurotransmitters listed and their known links to major depressive disorders, the primary neurotransmitter(s) involved in major depressive disorders are: f. Serotonin and Norepinephrine These two neurotransmitters are widely recognized for their roles in mood regulation and their imbalances contributing to depressive disorders. Many antidepressant medications specifically target these neurotransmitters to alleviate depressive symptoms.