The definitive guide to what is a mental illness and what is normal behaviour is due for release at the end of the month.
Previous additions to the tome have been ADHD and body dismorphia.
"Until it is in the book," said the Handbook's editor, Alan Talon, "it is not a recognised mental illness. Once it is in, pharmaceutical companies will research medication for it and psychologists can label people for life."
A leaked memo has indicated that obsessive compulsive disorder (OCD) has been sub-categorised, with train spotting specifically mentioned.
"It is true that we have identified train spotting as a form of OCD," said Talon. "Decades of research on train spotters have confirmed this as true. Besides, I saw the movie, and that was a seriously disturbed piece of cinema."
According to Talon, train spotting had always been considered a form of OCD, but the study revealed that it also contained a large dollop (technical term) of compulsive completist syndrome (CCS) and Aspergers Syndrome (Aspergers Syndrome).
"We have separated it out because of its combined factors," said Talon. "In the same we we split hoarding out from CCS because it has a small dollop of Abandonment Disorder."
Now that train spotting is a specific mental illness in its own right, it will not be long before it can be diagnosed and treated.
"We have fully documented the symptoms," said Talon. "These include an inability to become bored, being impervious to the cold, excellent circulation and a welded on raincoat. Psychologically, train spotters are very similar to well adjusted folk, however, they get a dopamine buzz from seeing a train that is in all respects identical to every other train they have ever seen apart from the colour of a wheel nut. Oh, and they don't know how to deal with people."
Big Pharma are already moving into the field in anticipation of the Handbook's release. It is anticipated that a cure for train spotting could be available as early as next March. Glaxo-Beecham-Proctor are to deliver it to towns in a custom made Diesel Electric locomotive to ensure the maximum number of customers.