By David Peter
BBC One's The Innocents
The cause of Chris Shorten's mental health problems probably date back to a time before he was even born.
Chris has problems with aggression
He is physically and verbally aggressive, finds it difficult to understand what people are saying to him, and has problems managing his money.
The condition he is thought to have is estimated to affect one in 100 people, yet most people have never heard of it.
Foetal Alcohol Spectrum Disorder (FASD) is caused by mothers drinking alcohol when pregnant.
It is thought that exposure to too much alcohol can damage the front of a developing baby's brain.
Resulting symptoms include learning difficulties, problems processing information, poor judgement, a lack of emotional control and an inability to control sexual impulses.
One form of FASD is known as Foetal Alcohol Syndrome (FAS).
People with FAS not only have behavioural problems, they also show signs of tell-tale physical characteristics, such as narrow eyes, a flattened philtrum (space below the nose) and a thin top lip. It is caused by heavy drinking during pregnancy.
Some medical experts believe that FAS could affect one in 1,000 babies.
In Britain, it is only the full version of the disorder which is officially recognised, and even then it is under-reported.
Figures suggest there were 150 cases last year, out of approximately 675,000 live births, but the World Health Organisation estimates that there were between 470 and 880.
Now, experts think there could be 10 times this number with some form of FASD.
Chris' mother, Tracey Hayter, admits that she drank heavily while pregnant with him.
"I'd have a bottle of wine for breakfast, a bottle of wine at night. This was quite a common thing."
Government guidelines on safe drinking advise women either to stop drinking altogether when pregnant or to stick to just one to two units of alcohol once or twice a week.
Tracey drank after Chris' father walked out
Chris has been having to deal with the knowledge that his disability was probably caused by something his mother did.
Moreover, he has to live with his disability itself. A 20-year-old with FAS has the reading ability of a 16-year-old, the money management skills of an 11-year-old, the emotional maturity of a six-year-old, and an average IQ of 80.
When Chris stays at his mum's house trouble can often ensue. Chris explains: "I've been in the house and I've pulled knives about and I've been violent, but I've not realised I've done it.
"But sometimes when the police turn up I'll think 'oh I've done it', but then sometimes it's too late because then they take you to the station and go through all that, and then you end up more angry because you realised what it is you've done."
But until his condition is recognised, he is just another young man on the housing list, flitting between bed and breakfast placements where he finds it hard to keep to the house rules, crashing on friends' sofas, or even breaking into cars just to have somewhere to lie down for the night.
It has always been believed that FAS and FASD can only be caused by heavy drinking in pregnancy, but there is an increasing body of opinion now stating that low to moderate drinking (as little as a couple of drinks twice a week) may be enough to harm an unborn child.
Dr Raja Mukherjee, a psychiatrist specialising in FASD at St George's, University of London, says: "One or two units is ambiguous. People don't drink one to two units; they drink more.
"How quickly can you drink one to two units? Is it safe for everybody - big or small, different sizes of people, who we know metabolise alcohol in different ways? Is it safe to say that for every single person out there, every single person that is pregnant, that they can drink that level?
"I don't agree. I think the only guaranteed safe message is to say that, if you can avoid it, don't drink."
"Don't drink" is the message that pregnant women in the US and Canada receive.
The current UK Government guidelines were published in 1995, but a report due in 2006, commissioned by the Department of Health, is looking into whether there is enough evidence to suggest the advice should change.
Chris and his mum, desperate to get him diagnosed so he can receive proper support, have now sought the advice of Dr Mukherjee.
The diagnosis he gives is astonishing, and both Chris and Tracey know that it will change the course of their lives.
The Innocents, part of BBC One's series Britain's Streets of Booze, was first broadcast on Wednesday, 5 October, 2005, at 0915 BST.