What is the brain’s role in OCD?

Researchers are still unravelling the mechanisms in the brain that are involved in OCD. It is very likely that OCD is not caused by changes to one single brain process, but instead, it appears due to changes in a number of different brain mechanisms. 

As we explored in the previous section, the brain and its development is influenced by several factors, including genes, environment, experiences, and behaviours. These all contribute to the unique structure and way that each person’s brain works.

It is likely that OCD arises when several brain processes develop in a certain way. Although the causes might be different between people, very similar symptoms (obsessions and compulsions) may appear. This is similar to why people might experience a headache, for example. A headache is a symptom (your head hurts) that may be caused by various things. It could be because of a migraine, too much sun, or consuming the wrong substances. Similarly, there might be different reasons why someone experiences OCD symptoms. In this section, we will explore the role of frontostriatal loops, which are at the centre of one of the long-standing scientific theories of what causes OCD.

Over the past few decades, researchers have come to believe that changes in frontostriatal loops lie at the core of OCD. These loops are important for prioritising and processing information.

In OCD, researchers think that when the control of this information flow is disrupted – for example because of an imbalance within the frontostriatal loops – OCD symptoms such as obsessions and compulsions may appear. 

• For example, if the control of a signal about a movement action is disrupted, this may lead to the person having urges to perform movement actions when they come across an OCD-related trigger (e.g. a stove, knife, or light switch). This results in compulsive acts being performed (eg checking the stove is turned off, avoiding sharp objects, turning a light switch on and off). 

• Similarly, an imbalance in frontostriatal loops can turn common intrusive thoughts into obsessions. Many people, with and without OCD, often experience intrusive and distressing thoughts. However, in people living with OCD, these intrusive thoughts tend to stick in the mind and are challenging to dismiss. This is where the frontostriatal loops once again are thought to play a role. If the loops have an imbalance, the brain might not be able to suppress the thought intrusions and dismiss them as irrelevant. As a result, the thoughts may stay present and become obsessions. Often, this leads to increasing levels of distress, and continues the cycle of performing compulsions to try to reduce the thoughts and distress that have become overwhelming.

In summary, researchers believe that difficulties in switching between processing different types of information or suppressing the flow of information in the brain can lead to people experiencing ongoing obsessions and compulsions. 

Going back to our traffic comparison, imagine if the timing of the traffic lights is off at a busy traffic junction. The junction would no longer be managed effectively and there would be disruptions in the traffic flow. For example, if a particular traffic light rarely switches to red, the traffic on that lane will get priority, causing major traffic jams for the other lanes. Even minor imbalances in such a complex and dynamic system can have significant consequences downstream.

Although there has been great progress in this area of research, exactly how the regulation of the frontostriatal loops becomes imbalanced is still being actively looked into. Similar to complex traffic junctions in big cities, in the brain, this balance can be altered in many different ways: 

1. Imbalances of brain chemicals (called neurotransmitters) which regulate these loops may play a role. 

2. The strength of the connection between brain areas may also influence the overall flow. 

3. Or changes can happen if the balance between the different loops is off. 

Because the frontostriatal loop imbalances may be caused by such different things, this may be one reason why some people benefit from one type of treatment, whereas others benefit from another approach. Researchers are actively looking into this – you can find out more in the next section.

The emergence of OCD symptoms

OCD symptoms often start to emerge either during late childhood, adolescence, or in the early twenties. Researchers think that because the brain undergoes lots of development during this time, there is a lot of room for certain brain systems to change in various ways. Both neurotransmitters and brain regions linked to the frontostriatal loops mature well into adolescence and even early adulthood. Therefore, if the development of these brain systems goes awry, this is likely to play a significant role in triggering the start of OCD. As such, the unique development of the brain may result in OCD. However, it is also important to note that OCD can manifest at any stage of life, often triggered by significant stressful events.

Researchers are still uncertain about why obsessions and compulsions focus around such diverse themes, ranging from health-related washing compulsions to uncertainty checking and harm avoidance mental rituals. It is possible that imbalances in frontostriatal loops may particularly affect things that someone considers most stressful, anxiety-provoking, or personally significant. In other words, the specific content of obsessions and compulsions may vary, and they may align with what certain people prioritise or care about the most. This would mean that even if the type of OCD is different, the biological causes might still be similar.

In summary, when looking at how brain networks work, OCD is likely to be caused by changes in frontostriatal loops, which are critical for prioritising and suppressing information flow in the brain. When there are imbalances in regulating this information flow, it may result in the development of obsessions and compulsions. Researchers are actively studying the specific processes within these frontostriatal loops that can be changed, the different things that might cause these imbalances, and what treatments might be effective in addressing these imbalances.