On the other hand, marijuana has been used to treat those symptoms. It may be your friend had some other problem that was being masked by the prolonged marijuana use.

Or one of the other many reasons why there can be correlation without causation.

The headaches are caused by the brain not producing its own canabinoids due to the influx of outside cannabinoid sources.

Source - lifelong medical cannabis patient.

I've been physically addicted to alcohol and opiates, and also a long term daily marijuana user (currently over a year of sobriety from all drugs). THC has no physical withdrawal symptoms.

And I've been drinking alcohol every weekend the last 15 years. Your alcoholism is a myth because otherwise I would need alcohol right now. It doesn't really work that way.

There's a difference between physical and psychological addiction.

Currently we think cannabis is not physically addictive, and we think it might be psychologically addictive for some people.

People de-toxing from alcohol addiction can literally die if they do it wrong. That's never going to happen with cannabis.

I was drinking at least a fifth (750ml) of 40% abv spirits every day, doing at least 250mg+ oxy or equivalent in heroin, or smoking a gram or more of weed a day. Alcohol and opiates are physically addictive with very real withdrawal symptoms. Falling asleep was somewhat difficult for a couple days when I ran out of weed. Marijuana is not physically addictive.