SSRIs are commonly used in the treatment of OCD. This is because malfunctions in the worry circuit are believed to be linked to low levels of serotonin, potentially due to abnormalities of the SERT gene, which codes for serotonin transporter molecules. 

SSRIs can take a long time to work for some people yet others experience relief in as little as 4 weeks. This study explores cognitive factors which might help to predict the time required for SSRIs to take effect. As cognitive psychologists such as Rachman (1993) believe dysfunctional beliefs lead to the development and maintenance of obsessional thinking, Park et al. decided to see whether a person's beliefs about their own thoughts (called meta-cognition) reliably predict the time taken for SSRIs to take effect. They were interested to see whether any specific beliefs correlated with early/delayed response, arguing that ultimately SSRI efficacy could be improved by simultaneously targeting dysfunctional beliefs using cognitive therapy.

Park et al (2020) carried out a prospective, correlational study to investigate the link between the way in which people perceive the value of their worry and how long it takes for SSRIs to be effective in the treatment of OCD. To measure the reduction of symptoms over time, researchers used the Y-BOC. To measure their thoughts about worry, the researchers asked participants to complete a 65 item questionnaire prior to treatment. Participants rated statements on a four-point Likert scale from do not agree to agree very much.

The questionnaire asked participants to rate the following types of statements:

•  Worrying helps me to cope

•  My worry is dangerous for me

The sample comprised 132 participants with OCD, aged 19-50, recruited from outpatient clinics in South Korea.

Participants were tracked for four weeks following the commencement of daily SSRI medication. The most common prescriptions were escitalopram and fluoxetine.

40.2% of the sample were classed as early responders (i.e. symptoms reduced by at least 20%) and the researchers identified two variables which were the best predictors of early response.

• Age: Younger people were more likely to improve by at least 20% over the four-week study than older people, (p < 0.001).

• People who ‘agreed very much’ with statements like ‘worrying helps me to cope’ were less likely to show early response to treatment than people who disagreed with this statement, (p = 0.001).

The researchers concluded that positive beliefs about worry were associated with delayed response to SSRI treatment for OCD. They suggest that these beliefs increase psychological resistance to SSRI treatment response and contribute to the maintenance of obsessive-compulsive symptoms. Furthermore, the motivation to stop worrying may be lower due to fear, as ceasing to worry may lead to failure to cope.

Since people who believe that worrying is counterproductive respond more quickly to SSRIs, the researchers suggest an eclectic approach to treatment, combining cognitive and pharmacological intervention may be the best option for people with dysfunctional beliefs.

The findings have real-world applicability. People who are unlikely to experience relief from SSRIs could be identified through meta-cognitive screening and supported appropriately before they begin to take their medication or prescribed a different type of medication that may allow for a quicker reduction in symptoms.

The researchers ensured that participants were drug-naive or had been drug-free for at least 12 weeks, meaning that the true impact of the SSRI was not influenced by the lingering effects of any other medications.

An important confounding variable could be that the participants did not all take the same SSRI. Some SSRIs may be more beneficial than others for the subgroup of people with positive beliefs about worry; this said, there was no significant difference in the type of SSRIs used by the early responders and non-responders, suggesting the findings could be generalized to people taking different types of SSRI.

The study only tracked participants for four weeks, but this was based on findings from previous research suggesting that four weeks is an important threshold in terms of potential future improvement.

Findings may not be generalizable as all participants were ethnically Korean.  There may be variables particular to this group that could influence the effectiveness of treatment - for example, family support, cultural stigma, or cultural attitudes toward the value of rumination and worry.