Which condition is a common indication for the use of tricyclic antidepressants (TCAs)?

Tricyclic antidepressants (TCAs) are primarily used to treat major depressive disorder because they are effective in increasing the levels of neurotransmitters in the brain, particularly norepinephrine and serotonin. This adjustment helps to improve mood and alleviate symptoms associated with depression.

In the case of major depressive disorder, TCAs can be particularly beneficial for patients who may not respond adequately to other types of antidepressants, such as selective serotonin reuptake inhibitors (SSRIs). They are often considered when a patient presents with severe or chronic depression that does not improve with first-line treatments.

While the other conditions listed can be treated with various types of medication, they do not necessarily indicate a primary use for TCAs. Bipolar disorder may involve mood stabilization with different classes of medications, schizophrenia often requires antipsychotic treatment rather than antidepressants, and obsessive-compulsive disorder usually responds well to SSRIs or cognitive-behavioral therapy. Thus, major depressive disorder stands out as the common indication for prescribing TCAs.