How Does White Matter Structure Change in Children with OCD?

What you need to know

• Diffusion tensor imaging studies show widespread white matter changes in children with obsessive-compulsive disorder (OCD).
• Key areas affected include the corpus callosum, cingulum, and white matter tracts connecting frontal, parietal and temporal brain regions.
• White matter changes correlate with OCD symptom severity and may reflect abnormal brain development in pediatric OCD.
• Findings are inconsistent across studies, possibly due to differences in methods, small sample sizes, and the complexity of OCD.

Brain structure and function in OCD

Obsessive-compulsive disorder (OCD) is characterized by recurrent, intrusive thoughts (obsessions) and repetitive behaviors or mental acts (compulsions) that a person feels driven to perform. OCD affects about 1-3% of children, with symptoms often appearing around age 10.

For many years, researchers have been trying to understand the brain basis of OCD. Early theories focused on problems in a brain circuit involving the orbitofrontal cortex, anterior cingulate cortex, and striatum. This circuit is involved in detecting errors or conflicts and regulating behavioral responses. More recent research suggests OCD likely involves more widespread brain changes.

Advances in brain imaging techniques have allowed researchers to examine the structure and function of the brain in people with OCD. One important method is diffusion tensor imaging (DTI), which can measure the structure and organization of white matter in the brain. White matter contains the fibers that connect different brain regions, allowing them to communicate. DTI provides information about how well-organized these white matter tracts are.

Key findings on white matter in pediatric OCD

This review examined 15 studies that used DTI to compare white matter structure in children with OCD to healthy children without OCD. The key findings were:

• Widespread white matter changes in children with OCD, particularly in:

  • Corpus callosum (connects the two brain hemispheres)
  • Cingulum bundle (connects frontal and parietal regions)
  • Tracts connecting frontal, parietal and temporal regions

• Both increases and decreases in measures of white matter organization were found, depending on the specific brain area and study.

• White matter changes correlated with OCD symptom severity in some studies.

• Changes were seen in major white matter tracts as well as more localized areas.

• Some studies found changes in white matter connecting regions not traditionally associated with OCD, like the occipital lobe and cerebellum.

White matter changes and OCD symptoms

Several studies found correlations between white matter structure and OCD symptoms or severity:

• Higher white matter organization in tracts like the cingulum bundle was associated with more severe OCD symptoms in some studies.

• Different symptom dimensions showed distinct patterns of white matter changes. For example:

  • Contamination/washing symptoms were linked to changes in midbrain, thalamus, and cerebellar regions.
  • Harm/checking symptoms were associated with changes in the corpus callosum and cingulate gyrus.

• Better white matter organization in some tracts correlated with better cognitive functioning in children with OCD.

These findings suggest abnormal development of white matter connections may contribute to OCD symptoms, though the relationships are complex.

Inconsistent findings across studies

While the overall evidence points to widespread white matter changes in pediatric OCD, there were many inconsistent findings across studies. Some key issues:

• Both increases and decreases in measures of white matter organization were reported, sometimes in the same brain regions.

• Not all studies found significant differences between OCD and control groups.

• The largest study, from the ENIGMA consortium, did not find any significant white matter changes in children with OCD.

• Studies varied in which specific white matter tracts showed differences.

There are several potential reasons for these inconsistencies:

1. Small sample sizes in most studies, limiting statistical power

2. Differences in DTI methods and analysis techniques across studies

3. Variability in OCD symptoms, severity, and comorbidities across patient samples

4. Effects of medication, as many patients were on OCD medications

5. Differences in age/developmental stage of participants

6. The complex nature of OCD, which may involve multiple subtypes with distinct neurobiological profiles

Conclusions

• DTI studies show evidence of widespread white matter changes in children with OCD, particularly in major tracts connecting frontal, parietal and temporal regions.

• White matter alterations correlate with OCD symptom severity and may reflect abnormal brain development.

• However, findings are inconsistent across studies, highlighting the need for larger, well-controlled studies of specific OCD subtypes.

• Future research should examine how white matter changes over the course of OCD development and treatment to better understand their role in the disorder.

While brain imaging studies provide important clues about OCD neurobiology, more work is needed to translate these findings into improved diagnosis and treatment. Continuing advances in imaging techniques and large-scale collaborations may help clarify the complex brain changes involved in pediatric OCD.