Basically – you might have a mental illness if you have feelings, thoughts or perceptions that get in the way of your life. You can have negative feelings or even see things and hear things that aren't there - but if it doesn't bother you then it's not a problem. Getting in the way means that your emotional experiences interfere with friendships, relationships, school or work, concentration or just getting things done that you want to get done.
To have a mental illness – your experiences can’t come from other physical health changes (like puberty, hormones, brain injury, seizures, inflammation issues) or because you are using drugs.
Physical health changes like puberty also correspond with wild mood shifts. For girls – you should keep track of your moods in monthly cycles. If your mood shifts around ovulation and your period – then your mood is better explained by hormone shifts and not mental illness. But, if you feel depressed for at least 2 weeks straight or feel anxious all the time – then it might be mental illness. For boys – same thing – keep track of your shifts in moods – are there patterns? If you feel depressed for at least 2 weeks straight or feel anxious all the time – then it might be mental illness.
Many physical illnesses can affect the brain or result in having additional mental health problems – because being sick sucks and your brain is connected to your body. The best way to figure out what to do, is to ask yourself what works. For people who have health conditions that effect their brains – sometimes treating their physical illnesses helps make their mental health problems go away. For others – even though their physical illness is treated, they’re left feeling emotionally horrible. If this is the case, then adding mental health treatments (talking to someone, medication, exercise, good food, digging deep to figure out what’s going on in your heart and mind) can help.
Using drugs can cause depression, anxiety, paranoia, and hallucinations. If you started feeling bad first and then used drugs to deal with it, you may have a mental illness and were self-medicating with drugs. The only way to get better is to get sober and see what experiences are left afterwards. Unfortunately, if you used drugs for a long time – it might mean that your body and your brain need time to heal. Just like exercise, this takes time and effort, but the end result is reclaiming your life.
Check out this article if you're wondering, "What is a mental illness?"