Introduction

The cognitive-behavioral model of insomnia proposes that arousal, cognitions, behaviors, and perceived consequences play an important role in maintaining insomnia symptoms. The metacognitive model of insomnia expands this idea by defining cognitive activity as primary arousal and how one interprets those thoughts as a secondary arousal. Because primary and secondary processes mutually influence each other, the content of maladaptive sleep-related thoughts can impact the maintenance of insomnia disorder more strongly if one is rigidly attached to them.

Methods

Data were collected from online surveys responded by 629 adults, aged 18 to 59 years, who reported experiencing insomnia symptoms. Participants completed self-report questionnaires, including:

1. Hospital Anxiety and Depression Scale (HADS);
2. Insomnia Severity Index (ISI);
3. Dysfunctional Beliefs and Attitudes about Sleep Scale (DBAS-16);
4. Acceptance and Action Questionnaire (AAQ-II).

All continuous predictors were standardized prior to data analysis. A linear model (estimated using OLS) was fitted to predict ISI scores from DBAS-16 and AAQ-II with age, sex and HADS subscales as covariates:

\[ ISI \sim Age + Sex + HADSA + HADSD + DBAS\times AAQII \]

Results

Figure 1: Distribution of continuous variables in the model.

The results of the regression indicated that the model significantly predicted ISI scores (F(621, 7) = 42), p < 0.001, \(R^2_{adj}\) = 0.31), accounting for 31% of the variance.

Figure 2: Decomposing dysfunctional beliefs about sleep by psychological inflexibility interaction via simple slopes for psychological inflexibility.

Conclusion

Insomnia severity scores were influenced by higher scores on anxiety, dysfunctional beliefs about sleep and psychological inflexibility. The significant interaction effect indicates that the prediction effect of dysfunctional beliefs about sleep may become more positive for additional levels of psychological inflexibility.