Samuel Johnson once urged his readers: "Look around. Tell me which of your wants is without supply. If you want nothing, how are you unhappy?" It's a reasonable question but even the legendary lexicographer could not find the words to answer it. For Johnson – respected, feted and wealthy – could never shake off what became an obsessive inability to be at ease with the world.
Even his gift for the written word could not help him. "It came into my mind to write the history of my melancholy," he haltingly set down. "I purpose to deliberate; I know not whether it may too much disturb me."
Biopsychology academic Dr Frederick Toates must have experienced similar fears before writing Obsessive Compulsive Disorder, an intensely personal work combining his battle with the same condition with strategies for trying to overcome it.
For Dr Toates has spent years trying to cope with irrational fears of almost impossibly unlikely disasters. We all doubt occasionally that we closed the front door, or turned the oven off. But few of us have refused to buy grapes for fear they have been poisoned by the CIA. Or, as teenagers, been scared to start university in case we began a doomed love affair. Or torn open an envelope we were about to post, fearing we'd put the wrong letter inside – then realised it was the right letter, gone home, written a fresh envelope and then got to the postbox to face exactly the same dilemma.
Dr Toates is honest about his emotions when recalling these demons. "I was afraid to write this book," he says. "Setting down dark thoughts keeps them on your mind."
Half of this recently revised work, first published in 1990, details fears that meant even the simplest tasks threw Dr Toates into a state of morbid terror. "I'm satisfied I wrote it," he says evenly, indicating how joyless a task it was. "When I returned to it 12 years later, some chapters were still difficult. There was no catharsis."
Dr Toates, now 59, recalls his problems began in his early twenties while teaching in Denmark. A period of euphoria was followed by inexplicable depression. "I tried to explain [to a girlfriend, Mette] that it was because life was so good that I felt so sad," Dr Toates writes, adding: "But this inverse logic made little sense to her."
As he slid deeper into depression, even touching Mette would ignite worries about her future. And he felt compelled to check everything. And then check it again. In the mid-Seventies, he hit rock bottom.
His fight back to health was boosted by a job at the Open University, where he still teaches as a renowned motivational theorist. But he admits that, 25 years on, he is no more "cured" now than he was then. "I'm like a diabetic who remembers his insulin," he says. "Danger is always lurking."
This new edition, written with his wife Dr Olga Coschug-Toates, suggests coping strategies including hypnosis, prayer, exercise and having constant company. But he knows they will not work for everyone.
"It's about getting by," he says. "When I go out I shut my door while saying the name of the place I'm visiting. If I doubt later on that I shut it, I'll remember that. And I'll still believe I've dropped a letter instead of putting it in a postbox – but now I can blame such confusion on growing old."
Dr Toates is grateful his career has allowed him to explore the condition, but even that raises inevitable questions. "Does the study of psychology make you madder than you would have been?" he says. "Certainly it's a subject which centres far more around misery than happiness."
And he accepts now that the melancholy will probably never leave him. "The frustrating thing," he says "is that I could be indescribably, blissfully happy, if only I wasn't neurotic. Take that away and I'm there."
'Obsessive Compulsive Disorder (Second Edition): Practical, tried and tested strategies to overcome OCD' is published by Class Publishing (www.class.co.uk), £14.99