No, mental illnesses aren't real, are they?

Did you know, 25% of the UK population will experience a mental health problem in any given year? 20% of the older generation will experience depression in any given year and roughly 10% of children will be suffering a mental health problem at any given time. With statistics this high, why is there still such stigma attached to mental illness? 
Suicide is, believe it or not, the leading cause of death among men under the age of 35 (Five Years On, Department Of Health, 2005). 3 years ago, more than 5700 people committed suicide in the UK. These figures are astounding, and I'm finding it so hard to understand why people don't take mental health seriously. One often hears misinformed people saying that people with mental health problems are only 'doing it for attention', and that there is nothing wrong with the sufferer. If this is true, then why is it estimated that only a quarter of people in the UK with a mental health problem actually seek help? I think, the stigma attached to mental illness (there in the first place as a result of misinformation and those with rather narrow minds, refusing to allow themselves to accept the facts and figures of mental illness...) does no help for that 75% who refuse treatment or do not feel they are in need of help. People who feed stigma have no idea how debilitating living with a mental illness can be. 
Mental illnesses have the power to control somebody's life. They're like parasites, eating your happiness, your sanity, and turning you into a thing, no longer a person but a thing. At my worst, I wouldn't leave my bed for anything. I would vegetate, my mind and body lacking the exercise they both so badly needed I turned into a shell of a being. Anybody who had the displeasure of spending time with me would know what an absolute state I was in. I missed school (though not much, as for a long time I refused to let anybody know the extent to which I had been taken over by depression), I stopped seeing my friends, I didn't sleep and mostly I lay in bed staring at the ceiling. Now, that is only speaking for somebody with depression, and even then not every sufferer is the same.  
If you are somebody who thinks depression is not a real illness, or mental health sufferers do it for attention, ask yourself: why? Why would somebody do that? Because it's fun? Surely not, it's anything but fun. Mental illnesses are no joke, they are real, painful and inexplicably horrific for the sufferer. The sooner people realise this, the sooner people can get the help and support they need.