Hi, I can understand your concern. One needs to deal with the withdrawal effects of medication and this is probably what your son is experiencing. This is the reason a psychiatrist would recommend gradual reduction of dosage than a sudden withdrawal.
Next Steps
However, your son can take certain steps to substitute for the effect of medication like including a physical activity in his routine, meditation, counseling sessions, following a specific routine in his daily life etc.
Health Tips
Here are some resources that you might find useful: https://www.madinamerica.com/drug-withdrawal-resources/. Good luck and if you have any other questions, please feel free to consult me.