Even if it could help them, there are risks[0], and in most jurisdictions, LSD is a highly restricted drug which doctors cannot prescribe therapeutically, so there is no guarantee of dose or purity. People with severe depression who would entertain this seriously are already prone to impulsive behavior and cognitive difficulties. The suggestion is irresponsible.

[0] https://medlineplus.gov/ency/patientinstructions/000795.htm