First I suggest he take a melatonin sublingusl and a small dose of vitamin e before he goes to sleep. Melatonin can get depleted in heavy cannabis users and it will free him from the most severe withdrawal symptoms while typically mild can be serious for an individual with phase shifted insomnia. And nudge him to consider to delaying use to later in the day, sort of like the Navy notion of not drinking until the Sun is under the arm. There is a chicken and egg like thing is he sick from cannabis or does he abuse cannabis because he is sick. I had issues when I was younger as I'm a type 1 diabetic and I became dependent on it. It didn't wreck my life but if I ran out I had horrible insomnia and other symptoms like slightly elevated body temp. Once I started melatonin I was able to moderate and stopped regular use. Some other ideas are sunlight on the eyes 20 min three times a week. That loads an enzyme that helps serotonin production. I've heard essential fatty acids help with hyperactivity in children they help the body put stuff on the nerve sides that sort of insulates them, maybe they could help? And final idea maybe a short trip with something like outward bound. Best wishes with your family helping him to move on with his life.
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