What exactly are you referring to in terms of 'poor mental health'?
Because from an Islamic perspective, those who are not of sound mind are not accountable for their actions.
Narrated Ali ibn AbuTalib:
The Prophet (ﷺ) said: There are three (persons) whose actions are not recorded: a sleeper till he awakes, a boy till he reaches puberty, and a lunatic till he comes to reason.
Abu Dawud said: Ibn Juraij has transmitted it from Al-Qasim b. Yazid on the authority of 'Ali from the Prophet (ﷺ). This version adds: "and an old man who is feeble-minded."
Grade: Sahih (Al-Albani)
Reference: Sunan Abi Dawud 4403