One of the biggest barriers to diagnoses of brain disorders is that symptoms — particularly those of apathy — can be mistaken for depression, resulting in inappropriate treatment and poorer health.
An excerpt:
Understanding apathy is central in addressing current gaps treatment and prognosis. Research shows that symptoms traditionally associated with depression, such as reduced activity and social withdrawal, commonly manifest in people who have brain disorders but it does not always involve sadness or hopelessness, which are core features of depression.
Interestingly, in the linked paper, they mention:
The utility of selective serotonin reuptake inhibitors (SSRIs) for apathy in depression is unclear. The literature on the topic includes several case reports that described onset or worsening of apathy with SSRIs in depression