Is it permissible to pay zakat on money deposited in a bank, from which its owner benefits from meager interest that barely covers the needs of his psychologically ill self?

Zakat on capital in the bank is obligatory if a hawl (lunar year) has passed on it and it reaches the nisab (minimum threshold), and similarly for profits on which a hawl has passed, regardless of the owner's health condition. Paying zakat blesses and increases wealth. If the man is unable to manage his affairs, his guardian must pay the zakat. However, if the bank's transactions are impermissible, the money must be withdrawn from it, and zakat is obligatory only on the permissible capital. Usurious interest must be disposed of by spending it on the welfare of Muslims. The person responsible for this is the owner who is capable of managing his affairs, or his guardian.