He was unhappy and had been having "bad thoughts" - feelings that everyone hated him, that he was responsible for an undentifiable wrong.
He left school, with the promise of a place at art school, but the thoughts started to get really bad.
Recognising the signs
As he became further withdrawn from his family, his mother Sue - a mental health worker - began to recognise the signs of schizophrenia.
Taking LSD for a short time when he was about 16 had not helped.
He says: "I didn't understand the symptoms. I couldn't hold a job down and I couldn't settle into anything because my mental health was deteriorating.
"My relationship with my parents got very strained. I thought they hated me."
But despite Sue's training, getting appropriate help for Adam proved to be quite difficult.
Adam, who is now 23, said: "Initially health professionals are inclined to think that you are just going through normal teenage stuff, that it's your hormones.
"I knew that I wasn't going through a phase, that I felt out of control.
'Very hurtful'
"I was eventually diagnosed with paranoid schizophrenia when I was 17."
Sue found she could not continue to be a mental health worker because "it all became too personal".
She said: "He has said some very hurtful things to us - recriminations for things he thinks we have done to him.
"He will remember an incident when he thinks we did him wrong, and he will say things then."
Different things would - and still can - act as a trigger for one of Adam's episodes, where he wil experience extreme paranoia and negative thoughts.
"He even gets that he looks paranoid and suspicious, and he takes less care of himself, so that people do stare at him, and that just fuels his paranoia."
Adam knows this is true. He said: "One of my sisters has a heart condition and I know I wasn't coping well when she was ill.
"Even when I'm not really bad, I still have days when the bad thoughts come and I feel like breaking down and crying in the middle of the street."
He now lives in a flat in Watford, Hertfordshire where he is supported by a community mental health team. He also attends a day centre which holds relaxation and swimming sessions.
Plans for the future
Soon, he would like to be able to go back into education, or professional training.
But with a serious epidsode only a couple of months behind him, he knows he has got to take things one step at a time.
Before Christmas, Adam's life appeared so bleak to him that he made meticulously plans to take his own life.
Later, talking things through with a psychiatrist, he admitted he had planned different ways of ending his life - including jumping from a multi-storey car park.
What he ended up doing was walking to a garage, buying a gallon of petrol, and going into a police station.
He told the police he was responsible for the murder, then poured the petrol over himself and pulled out a cigarette lighter.
His mother says: "It didn't spark. He flicked it and it didn't ignite.
"The policeman dived over the counter and saved him. The police were so good, they recognised the situation and they saved my son's life."
The episode had been preceded by a change in Adam's medication.
Side effects of medication
Because he had been suffering "terrible" side effects from his previous drugs, he was taken into hospital while new medication was introduced.
"The result was that he got very depressed - and then I got the telephone call from the police station," said Sue.
She is hopeful for her son, but she worries that he may try to take too much on.
Adam is in regular contact with his family, and says he loves them dearly.
"We have had our ups and downs, and at times it has been incredibly difficult," said Sue.
"We found it very difficult to get the services and care that Adam needs - and if I as a health professional found it difficult, then other families must find it almost impossible.
"We really need as a society to be doing a lot more for these vulnerable young people.
"I am aware that if Adam had MS, people would be fundraising for him - but he is mentally ill.
"We have been lucky in very many ways, but it shouldn't be this difficult."