Major Depressive Disorder: Neurobiological Basis
Option B is correct: Major Depressive Disorder involves abnormalities in one or more biogenic amine neurotransmitters including dopamine, serotonin, and norepinephrine (noradrenaline). 1
Why Option B is the Best Answer
Neurotransmitter Abnormalities Are Central to MDD Pathophysiology
MDD is fundamentally associated with deficiencies in dopamine, serotonin, and noradrenaline neurotransmitter systems. 2, 3
The American College of Physicians guidelines explicitly state that second-generation antidepressants work through "mechanisms of action that selectively target neurotransmitters," specifically serotonin and norepinephrine reuptake inhibitors. 1
The serotonergic system has received substantial attention since the early finding that MDD responds selectively to serotonin reuptake inhibitors (SRIs). 1
Dopamine system dysregulation is increasingly recognized as underpinning MDD pathophysiology, with dopamine deficiencies thought to contribute to core symptoms. 2, 3
The noradrenergic system is a primary target of multiple antidepressant classes, including SNRIs and tricyclic antidepressants. 4
Why the Other Options Are Incorrect
Option A (Neural imaging does not show structural changes) is FALSE:
Structural brain changes ARE documented in MDD, including decreased hippocampal volume and alterations in multiple limbic areas. 1
While these changes may overlap with other psychiatric disorders, they are demonstrable findings in depression. 1
Option C (Children with depressed parents have no greater risk) is FALSE:
This contradicts established evidence about the heritable nature of MDD. 3, 5
MDD is explicitly described as a "heritable neuropsychiatric disease" with genetic contributions. 3, 5
Option D (Depression does not interfere with daily functioning) is FALSE:
The American College of Physicians defines MDD as requiring "depressed or dysphoric mood that usually interferes with daily functioning (nearly every day for at least 2 weeks)." 1
MDD is "the second most common cause of disability worldwide" and "one of the largest contributors to chronic disease burden." 2, 3
Functional impairment is a diagnostic requirement, not an optional feature. 1, 6
Clinical Significance of the Neurotransmitter Model
The biogenic amine hypothesis directly informs treatment selection, with different antidepressant classes targeting specific neurotransmitter systems. 1
SSRIs target serotonin, SNRIs target both serotonin and norepinephrine, and bupropion targets norepinephrine and dopamine. 1, 4
Understanding that multiple neurotransmitter systems are involved explains why some patients respond to one class of antidepressants but not another. 2, 7