Have you locked the door this morning? Are you sure? If you feel the need to go back and check now, you are experiencing some of the key problems of obsessive-compulsive disorder (OCD): doubt, uncertainty and worry.



The difference between you and a person diagnosed with OCD is that you will check the door once. Afterwards, you will continue with your day, satisfied and calm. Yet, despite having checked 20, 30, or more times, an OCD patient may remain deeply unsettled. Believing for example, that his parents will die unless the door is locked properly, he can't stop until it "feels just right".



We all obsess about things every now and then, but usually our worries serve a purpose. Not giving burglars a chance, for instance. Obsessions and compulsions in OCD, however, are irrational. They dominate patients' lives, cause distress and make many of them unable to study or work. Therefore, OCD is not just a personal issue; it is also an economic problem for society. Treatments are available, but they only work for about half of the patients. If we are to develop more effective therapies, we will first have to gain a deeper understanding of the disorder itself.



My PhD project focuses on how OCD starts in the first place. More than 80% of the patients experience their first symptoms before the age of 18. However, most of the research has focused on OCD in adults. This group is usually asked to complete a few computer based tasks. Designed as puzzles or games, the tasks keep participants interested whilst producing important data that give us an insight into their abilities.



Researchers all over the world have identified key functions that are less developed in OCD. Suppressing a hand movement that has already started is one of them. If you were a participant in such a study, you would be asked to respond to an on-screen arrow by pressing a button as quickly as possible. However, when the arrow is followed by a "beep" you should not respond at all. While this sounds easy enough at first, the beep is delayed until you can't help pressing the button incorrectly. Afterwards, we can measure how much time between the appearance of the arrow and the "beep" you needed to reliably stop your hand movement. For OCD patients, this time is shorter than for healthy people. They are what we call "disinhibited", which might explain their difficulties with control in general.



Next, we will ask you to play another game. You see two patterns and must determine which one is 'correct'. After a few attempts you may spot a rule that allows you to succeed every time, but again, there is a surprise in store. Each time you learn the rule, the computer will change it, making it a little more difficult. Beginning as just purple shapes, the patterns become more complex as white lines are added. While irrelevant in the beginning, eventually you will need to learn a rule about these lines.



Healthy people are quite able to forget the old rules and to learn the new ones. However, OCD patients find it particularly hard to focus on the lines which they could previously ignore. They are stuck with the old solution to the problem and can't unlearn it. It might be the same kind of inflexibility in their every-day lives that requires them to check a door an excessive number of times to be sure it is locked… if they ever are sure.



There is a big controversy about whether adolescent and adult OCD are part of the same disease, or if they should be seen as two separate subgroups. The OCD symptoms reported in children and adults are similar and we treat them in almost identical ways: behavioural therapy and medication. Nonetheless, there are more male than female adolescent OCD patients, whereas there is a gender balance amongst adult sufferers. Moreover, while many patients of all ages have other issues in addition to OCD, it tends to be ADHD in teenagers, but depression in adults. This raises the question: are there fundamental differences between these two groups in terms of the OCD itself? Or do the adolescent patients grow up and still have the same less developed functions?



To test this, I will give the games you played in the fictional psychology lab to teenagers with OCD. If they are as disinhibited and inflexible as their adult counterparts, this suggests teen and adult OCD is the same mental disorder. If not, we might have to re-think our ways of treating adolescents with OCD and develop new therapies. Either way, we will understand how OCD starts in young people and what the key functions are that patients lack.



Max Perutz Science Writing Award



Inset image: Julia Gottwald