Reductions in the internalising construct following internet-delivered treatment for anxiety and depression in primary care.

Depressive and anxiety disorders are different manifestations of a latent internalising construct. To date, efficacy studies have tended to focus on disorder-specific outcomes, rather than underlying dimensions. This study examined the effect of a transdiagnostic internet-delivered cognitive behavioural therapy (iCBT) on the internalising construct in a primary care sample. Participants included 635 patients aged 18 years or over who were prescribed a six lesson transdiagnostic iCBT program for anxiety and depression by their primary healthcare professional. All patients completed the Patient Health Questionnaire 9, the Generalised Anxiety Disorder 7-Item Scale, the Mini Social Phobia Inventory and the Panic Disorder Severity Self-Report Scale at baseline. 325 of these patients completed the program and provided data on each of these scales during the final lesson. Reductions in the latent internalising construct were assessed within a longitudinal factor analysis framework that compared internalising factor means before and after treatment. The within group mean reduction in the latent internalising construct was large (ES = 1.23, SE = 0.09; p < 0.001). Due to the lack of a control group, between group reductions in the latent internalising construct could not be investigated. This study demonstrated that there are clinically significant reductions in the latent internalising construct following transdiagnostic iCBT for anxiety and depression.

Investigating differential symptom profiles in major depressive episode with and without generalized anxiety disorder: true co-morbidity or symptom similarity?

BACKGROUND: Large community-based epidemiological surveys have consistently identified high co-morbidity between major depressive episode (MDE) and generalized anxiety disorder (GAD). Some have suggested that this co-morbidity may be artificial and the product of the current diagnostic system. Because of the added direct and indirect costs associated with co-morbidity, it is important to investigate whether methods of diagnostic classification are artificially increasing the level of observed co-morbidity. METHOD: The item response theory (IRT) log-likelihood ratio procedure was used to test for differential item functioning (DIF) of MDE symptoms between respondents with and without a diagnosis of GAD in the 2001-2002 National Epidemiological Survey on Alcohol and Related Conditions (NESARC). RESULTS: The presence of GAD significantly increased the chances of reporting any symptom of MDE, with odds ratios ranging from 2.54 to 5.36. However, there was no indication of significant DIF of MDE symptoms in respondents with and without GAD. CONCLUSIONS: The lack of any significant DIF indicates that cases with GAD do not present with a distinct MDE symptom profile, one that is consistent with the endorsement of symptoms that are conceptually similar in nature between the two disorders, compared to cases without GAD. This does not support the hypothesis that co-morbidity between MDE and GAD is artificially inflated because of the similar symptom criteria required by the current diagnostic system. Instead, MDE and GAD may be thought of as two distinct diagnostic entities that frequently co-occur because of a shared underlying trait.