Finasteride not only decreases the conversion of testosterone into DHT but also nearly a dozen reactions as you can see here:
This study looked at PFS patients and determined that compared to healthy controls, they have altered levels of chemicals in the brain that are known to be affected by finasteride (dihydroprogesterone, DHT, allopregnanolone etc.)
As this blog posts seems to suggest, it is hypothetically possible that something else caused these “changes in the brain”, but it would be a very big coincidence that these PFS patients have abnormalities in the the exact chemicals that are already known to be affected by finasteride.
Taken note. Every drug you take has effects that go beyond what it is designed for. The FDA requires drug companies to identify as many of these side effects as can be identified. Clearly, the system is very far from perfect with the FDA and the drug companies and how they interact.