This will be long, sorry.
From what I know, it's misinformation when people say that it causes depression, social anxiety, schizophrenia, respiratory issues or any form of cancer. It's true that it can aggravate any existing respiratory issues if you're smoking it, rather than eating or vaping it, and it's true that it can aggravate your throat as well. but it does not and cannot cause cancer unless you are smoking it with tobacco mixed in. There is a chemical in weed that actually kills cancer cells, you can read about it if you find the unbiased scientific research on it.
It also doesn't cause any mental health issues. If you are someone with an underlying disorder that you do / don't know about, it can spark those neurons and begin to cause you symptoms, but the weed itself does not cause that. As for the unhealthy eating habits and lack of motivation- that depends on the type of weed you have (indica/ sativa) and the choices you yourself make. Not to mention, it helps a lot of people with PTSD and anxiety, as well as people suffering from ulcers, seizures, and illnesses like cancer. That's one of the main reasons people are trying to legalize it. In fact, my mom, a disabled vet, who knows at least a hundred + other vets, disabled or not, find that smoking a little greatly reduces their PTSD symptoms and anxiety related disorders, and almost all of them smoke.
As for the criminalization of pot- I think it it ridiculous and should be legalized. It is not harmful if used correctly and moderately. Most of the people in jail for it are nonviolent offenders, and the other people (dealers, suppliers) in jail for it are there because the system itself is broken. We should be looking at the whole reason people turn to supplying and selling drugs in the first place, and help prevent people from turning down that road.
Im not anti pot obvs. because I believe it's everyone's choice what goes in or on their body, and that includes drug use as long as they aren't hurting anyone else. I'm not going to keep going on about this, as this wasn't what the OP asked.

I've always had a love-hate relationship with pot. I've hallucinated pretty intensely on it in my earlier years, and I've been able to relax on it and get a different point of view on my problems that I wouldn't have been able to get without it. It was a nice escape when it needed to be, and it was a nice stress reliever when I needed it to be. (Everybody needs a method to forget, and everybody needs a method to remember. Escaping can be healthy sometimes.)
For a time, it did help with my PTSD and anxiety a LOT. I was able to socialize more than I ever would have without it, and I definitely didn't judge myself as harshly as I did when I was sober. Using it, I was able to discover parts of myself that I didn't know were there, getting a more complete picture of the person I was, am, and might become.
My problem was that I have an addictive personality (I can easily become an alcoholic etc due to genes). I used it more and more- both due to wanting to escape the thoughts of my problems and life completely, and because I was somewhat pressured by people I was close to and gave in easily to them. As I used it more often, my psychotic symptoms became more prominent, though I wouldn't figure this out until after quitting. As I used it and the negative things going on around me- being pressured, being depressed, stress from many directions- I started to lose my grip on myself. My anxiety became extremely difficult to control, and toward the last few months of use my delusional/ out of touch thinking got worse... I wouldn't be able to be around anyone and would go to my room until I wasn't high. I'd have to comfort myself because it was too stressful being so anxious and [seriously] tripping out over silly things. Depending on how high I got, the paranoia could come and go, or last shortly compared to my anxiety. If I was alone in the house sometimes the paranoia would lead to hallucinations, or if I listened to music... but that was when I smoked heavily.
The last time I got high I remember pretty clearly, and it put me off of it. I haven't smoked for a whole year and half now, and I've done my best to enjoy myself without it.

Granted, I found this thread because I was jonesing to smoke again.. If I decide to, I won't get high, probably just take one hit and leave it at that. Getting high might be a lot of people's problems- if they just took a few hits and kept it at a level they can handle, I'm sure there's be a lot less people overeating, feeling anxious, etc etc.

The main thing is: Everyone has different experiences with marijuana, and drugs, just like people experience daily sober life differently. If you want to smoke, read other people's experiences that don't have any mental illnesses, and some with the illnesses you might share. Know how to cope, just like you should know how to cope if you get too stressed or hallucinate, etc. Know your limits, know when you are in a healthy enough mindset to smoke, and be comfortable / have comforting things nearby. I find a shower really helps
There are also resources online for people having a difficult experience with it, or you can just search how to help.