In and of itself alone, a diagnosis of any sort would never deter me from being friends with or pursuing a relationship. What would worry me, and be a red flag, is anyone using medications to treat a diagnosed mental illness. From my experiences and of those in my family, I am against medications. Unless every cognitive, behavioral, counseling, (you name it) was tried and someone still wanted to try drugs to relieve symptoms, until then I would not support someone using drugs to suppress themselves. I have a very strong opinion on this.
This links into how I will not date anyone who uses recreational drugs or drinks alcohol. You can be my friend and do those things, but don't do them around me at all. And I do think a lot of people use alcohol way too much to cover up problems rather than deal with them.
I'm not against drugs for physical illnesses. And yes some mental illnesses possibly have physical roots, but in my experience drugs are only a bandage that needs to be reapplied every day. Being dependent on medication is never a cure. Not that I believe in cures, but someone who takes control of their own thoughts and actions with their own willpower (and support) is what I value and look for.
I would much rather talk with my partner and be part of helping them on a daily basis for any mental illness they may have. If they had a or desired to have a plan of action I would do all I could to help. I suppose the general advice you can read about on the internet says that how you handle yourself as a single person is important. And something along the lines of you should choose partners who can live alone and function fine by themselves. I see this type of advice and philosophy a lot, and I don't believe it at all. Humans are social creatures who need each other. How my partners are codependent on me, and vice versa, is something I want out of life. Hope that makes sense for anyone that reads this.
Mental illness IS physical illness. This is a false dichotomy. We don't have anywhere near a full understanding of the brain. But that does not change the fact that thought is a physical action in the brain. Feelings are biological, and have a physical reality. The emotional swings of a bipolar person are physical realities. The psychosis of a schizophrenic is not a failure of willpower.
The drugs used to treat mental illness can have terrible side effects. They are definitely over-prescribed, particularly for depression. We throw drugs at people when what they really need is a comprehensive support system. That is sadly lacking in the U.S. Non-drug treatments, lke the various types of therapy, alternative medicine - are not used enough or supported enough in our current medical system (assuming you are in the US). They can also be invaluable used in conjunction with drug treatments.
But it has been my experience that with some conditions, like bipolar, drugs save lives. Some mental illnesses do respond to non-drug treatments. Some don't. There are conditions where there are currently few effective drug treatments, like borderline personality disorder. And it varies dramatically from person to person. Some people with the less severe bipolar condition can treat it successfully without drugs. Drugs are useful to get a person back to a base of sanity, to stop psychosis. Talk therapy with someone in a full blown paranoid delusional state is an exercise in futility.
I personally find it worrisome when people discount drugs to treat mental illness. I get that you would encourage people to explore all options first, and that can work in many situations. But sometimes it doesn't and could lead to situations where the risk of death by suicide, out of control behavior, impulsive extreme risk taking, and so on. It has been my experience that people with bipolar - which is what I am familar with - who do not use drugs as an element in their treatment are more likely to fuck up their lives, if not outright kill themselves through behaviors like what I noted just above.
Mental conditions are also currently chronic illnesses. Medicine doesn't know enough about them to really offer cures. I hope that changes soon. They can be managed and treated but not truly cured - as in one never has to worry about them again. Someone with bipolar will not suddenly become not bipolar. They may not show symptoms for decades but the condition is still there. Someone with clinical depression will need to be cognizant of their mental and emotional health for the rest of their life. This is hard to cope with. People with mental illness don't get a break from dealing with their illness - they will need to deal with it for the rest of their lives. It is wearing and frustrating for them and for their partners.
I also agree that too many folks use drugs or alcohol to cover up problems. But it is possible to use alcohol responsibly. Unlike smoking or drug use, alcohol can be enjoyed in moderation without negative impacts. I do agree that our social attitude toward alchohol is all kinds of messed up and unhealthy, and encourages alchohol use as destructive coping mechanism.
I think some people can use some drugs, like marijuana, responsibly where it does not affect their life in a negative way. But others get addicted and have all kinds of poor outcomes. The reason that I encourage others not to use any drugs is that it is currently impossible to know which people can use responsibly and be fine and which people can't. Yes, some folks have family histories full of addiction and that is definitely a clear warning not to use alcohol or drugs. But for most of us, we don't know.