How Common Are Schizophrenia-Spectrum Disorders in Patients Diagnosed with OCD?

What you need to know

• Almost two-thirds of patients clinically diagnosed with OCD met criteria for a schizophrenia-spectrum disorder when carefully assessed
• One-third had current or previous psychotic symptoms that may have been overlooked
• “True obsessions” with full insight and resistance were specific to OCD, while “pseudo-obsessions” without resistance were common in schizophrenia-spectrum disorders
• Careful assessment of subtle schizophrenia-like symptoms is important when evaluating patients with apparent OCD

Background and purpose of the study

Obsessive-compulsive disorder (OCD) and schizophrenia-spectrum disorders can sometimes be difficult to tell apart. This is because some of the symptoms can appear similar on the surface. For example, both conditions can involve repetitive thoughts or behaviors that the person finds distressing.

However, correctly distinguishing between these disorders is very important for providing proper treatment. The researchers wanted to investigate how common schizophrenia-spectrum disorders might actually be among patients who have been diagnosed with OCD. They were particularly interested in looking for subtle signs of schizophrenia-like symptoms that may be easy to miss.

How the study was conducted

The study included 42 patients who had been diagnosed with OCD at specialized clinics. The researchers conducted very thorough psychiatric interviews with each patient, lasting 3-6 hours in total. They assessed for a wide range of symptoms related to both OCD and schizophrenia-spectrum disorders.

Importantly, they looked not just for obvious psychotic symptoms, but also more subtle disturbances in how patients experienced themselves and the world around them. These subtle symptoms, called “self-disorders,” are thought to be a core feature of schizophrenia-spectrum conditions.

After gathering all this information, expert clinicians made diagnostic assessments for each patient based on standard criteria. They determined what diagnosis (or diagnoses) best fit each patient’s full history and range of symptoms.

Key findings

The study uncovered some surprising results:

• 62% of the patients met criteria for a schizophrenia-spectrum disorder when carefully assessed. This included:
  • 28% with schizophrenia or another psychotic disorder
  • 33% with schizotypal personality disorder
• Only 29% were found to have OCD as their primary diagnosis
• One-third of patients had experienced psychotic symptoms at some point, which seemed to have been overlooked previously
• Subtle self-disorders were much more common in patients who met criteria for schizophrenia-spectrum disorders compared to those with only OCD

What are self-disorders?

Self-disorders refer to subtle but pervasive disturbances in a person’s basic sense of self and experience of the world. Some examples include:

• Feeling as if your thoughts are not really your own
• A sense that your body or parts of it are changed or alien
• Feeling as if the boundaries between yourself and the world are unclear
• Difficulty distinguishing between imagination and perception

While these experiences may sound unusual, they tend to feel natural or normal to the person experiencing them. This makes them easy to miss unless specifically assessed.

The importance of “true” vs. “pseudo” obsessions

The researchers also looked at the nature of patients’ obsessive thoughts. They distinguished between:

• “True obsessions” - Thoughts that the person recognizes as irrational and tries to resist
• “Pseudo-obsessions” - Intrusive thoughts that the person does not recognize as irrational or try to resist

They found that true obsessions were highly specific to OCD - 93% of patients with true obsessions had OCD as their primary diagnosis. In contrast, pseudo-obsessions were much more common in schizophrenia-spectrum disorders.

This distinction may be helpful for clinicians in distinguishing between OCD and schizophrenia-spectrum disorders. Patients with schizophrenia may report obsessive-like thoughts, but often lack the insight and resistance seen in OCD.

Why were schizophrenia-spectrum disorders so common?

There are a few potential reasons why so many patients diagnosed with OCD were found to actually have schizophrenia-spectrum disorders:

1. Overlapping symptoms - Some symptoms can look similar between OCD and schizophrenia-spectrum disorders on the surface. Without careful assessment, the underlying cause may be misidentified.

2. Focus on obvious symptoms - Clinicians may focus on the most obvious and distressing symptoms (like compulsive behaviors) without fully exploring more subtle symptoms.

3. Changing diagnostic criteria - The official criteria for diagnosing OCD have broadened over time. This may lead to over-diagnosis of OCD in some cases.

4. Lack of assessment for self-disorders - The subtle self-disturbances common in schizophrenia-spectrum disorders are not routinely assessed in many clinical settings.

Implications for diagnosis and treatment

These findings highlight the importance of thorough assessment when evaluating patients with apparent OCD symptoms. In particular:

• Clinicians should be alert for subtle signs of schizophrenia-spectrum disorders, including self-disorders
• The nature of obsessive thoughts (true vs pseudo-obsessions) may provide important diagnostic clues
• A history of psychotic symptoms, even brief ones, should be carefully explored
• Patients diagnosed with OCD who do not respond well to standard treatments may need reassessment

Getting the diagnosis right is crucial, as the treatments for OCD and schizophrenia-spectrum disorders are quite different. Misdiagnosis could lead to ineffective treatment and poorer outcomes for patients.

Limitations of the study

While this study provides important insights, it does have some limitations to keep in mind:

• The sample size was relatively small (42 patients)
• All patients came from specialized OCD clinics, so may not represent all OCD patients
• The in-depth assessments were very time-consuming, which may not be feasible in many clinical settings

Larger studies in more diverse clinical settings would be helpful to confirm and expand on these findings.

Conclusions

• A high proportion of patients diagnosed with OCD may actually have schizophrenia-spectrum disorders when carefully assessed
• Subtle symptoms like self-disorders and the nature of obsessive thoughts provide important diagnostic clues
• Thorough evaluation beyond just the most obvious symptoms is crucial for accurate diagnosis
• Further research and refinement of diagnostic approaches may be needed to better distinguish between these conditions

This study highlights the complexity of psychiatric diagnosis and the importance of careful, comprehensive assessment. While categorizing disorders is useful, clinicians must remember that real patients often do not fit neatly into diagnostic boxes. A nuanced understanding of each individual’s unique pattern of symptoms is key to providing the most appropriate and effective care.