Depression is associated with low levels of serotonin and norepinephrine.
The correct answer is D. (Serotonin and norepinephrine). When someone is depressed, his or her serotonin and norepinephrine levels are lower than average. Serotonin is linked to mood and arousal. Norepinephrine, also known as noradrenaline, is also linked to alertness and arousal control. Insufficiency of both neurotransmitters links to depression.