Western definition of "mental illness" isn't used here in the East. Over there, being sad is down syndrome or depression, shyness is considered as social anxiety, sleeping less or going to bed late at night is called insomnia and trying to keep yourself and your surroundings clean and tidy is called OCD.
You obviously have NO idea as to what you are talking about. Did you get diagnosed and ran away to your country from US or the UK?
Allow me to share the BASIC definition of mental hygiene as I can speak with a lot of confidence on this topic. Let's pick two examples from your post and try to form scientific and clinical criteria. Being Sad is "Down Syndrome"?? Are you kidding me???
Down Syndrome is a genetics disorder where a woman, if she's above a certain age (typically over 35), has high risk of causing a genetic malfunction, which then results in a child that can't speak, has issues with their face, bodies, and these children can never look or talk like normal children. They are born with brain wiring done incorrectly as this gene is responsible for it. Resulting in a malfunctioning brain and deformed organs. Majority of these children in the East, die at some point, sadly.
Just so you now, the Down Syndrome patient / child can never communicate to you or talk like humans that you'd even understand if they are sad or happy. They can just show emotions through their facial expressions.
Next, I'll pick the last item, the Cleanliness issue. Keeping yourself and your surroundings clean is great. But let's define the criteria, is the person "constantly" cleaning your hand and body, like ten times a day or so, normal? You think taking 10 showers a day is being clean? Similarly, does the person doing so much cleaning, went through a loss recently like Divorce, lost family members, friends? or Hallucinates? Well, if any of these are present, then its not a typical "I want to be clean". Does the person get scared a lot or stay awake on majority of nights? or has nightmares every-time they try to sleep? or they talk to others or can get violent if things aren't done their way or keep thinking about an event and NEVER forget it (Classic sign of OCD and Mania)...?? These symptoms are WAY beyond "Normal" personality and require treatment, or they can harm themselves or others. If you know a person like this, and they didn't do anything like this, doesn't mean nothing like this happens.
Diagnostic and Statistical Manual of Mental Disorders, or as known in the US medical industry as "DSM" (version 5 is the latest, defines ANY mental disorder with symptoms that interfere with a normal daily life. DSM has all criteria which the healthcare professionals use to diagnose, identify and test, treat and manage mental disorders.
Sadness or depression due to an event like losing a friend, missing family, sad after a job loss, are normal human feelings. When someone becomes so sad that they lock themselves in the room for months, don't shave, don't brush their teeth or don't eat and get angry or sad or scares, you've crossed the "normal sadness and normal depression". Now you are considered clinically depressed and you'll need medication to go back to your normal life, or you'll keep going into more and more darkness.
Similarly, if a person taking 3 showers a day and washing hands 5 time or more, still manages a family, friends, work, and other obligations, and doesn't get violent, scared, doesn't hallucinates or doesn't lose sleep for weeks or months, is STILL considered a normal person.
People and the doctors in the West aren't stupid. No one just diagnoses you with something because they want to. There is a strict criteria for it. But Eastern countries like Pakistan, India, Bangladesh, Afghanistan, even in the ME, Russia and some other countries, mental illness is a myth and people spend their lives and ruin them, when they can live normally if they went to a Brain Doctor and took a pill or two for a while. Hiding disease is not equal to better health, trust me!!
So my suggestion is, not talk about these serious diseases if you don't know the clinical history, criteria and all. It just sounds stupid to write stuff on here that people go to Med school and then to specialty careers for, and spend over 10-12 years in learning about these diseases and how to fix them if they can!!