Brothers and sisters,
for looking out and caring for your fellow Muslims.
Brother White Falcon,
There are indeed mental illnesses which effect all people which should be treated wholistically- meaning they should be treated with conventional medical treatments as well as Islamic spiritual treatment and other compatible treatment plans.
But whatever the treatment plan, first there is a requirement of a professional with expertise to diagnose what is wrong with the brother. It is better for HIM to know what is wrong too. He can then choose how to face it.
It is wrong for Muslims to presume all mental illnesses are simply effects from poor spiritual development.
There are all kinds of causes of mental illnesses, including very practical causes. Late stage syphillis ( a bacterial infection) causes mental illnesses- hence an infection which can be cured with conventional medication can be a cause of mental illness ( dementia).
So too can a parasite. Toxoplasmosis, a parasite found in cat feces and uncooked, raw meat and vegetables, has been found to be connected to mental illness ( manic depression, schizophrenia).
Head injuries from a car accident, from childhood abuse, from boxing, etc. can also be found to be related to all kinds of mental illnesses.
Your friend needs to see a professional/expert in order to be able know what is happening to him.
Ask your friend why he doesnt want to see an expert.
Try to help him to think through the steps. While I am unfamiliar with Pakistani culture, very often patients struggling with mental illness sense their loss of control and fear it. They are often more afraid because they don't know.
Try to have him articulate his fears.
Please inform him that HE will be in control, and will be FREE to choose how to respond- but HE needs to know a diagnosis.
See if that comforts him. Then again, articulating fears of mental illness may not be something common in Pakistan and he will just resist.
If he is acting out violently, as in having a tantrum, then it may be a case that his family needs to act on his behalf.
And May Allah help you and cure your friend.