Combined Effect of TCC-I and BATD on Depressive Symptoms and Insomnia

The goals of this interventional study is to study if the combine effects of Behavioral Activation Treatment for Depression (BATD) and Cognitive Behavioral Therapy for Insomnia (CBT-I) is effective on primary outcomes : depression, insomnia, well-being and anxiety and secondary outcomes : worry, rumination, behavioral inertia, experiential avoidance, anticipatory pleasure deficits, cognitive resource deficits, emotional reactivity, quality of sleep, and sleep beliefs for participants suffering from depression and insomnia disorders.

Depression is a widespread mental disorder characterized by affective, cognitive and physiological disturbances that impact individuals' daily functioning. Sleep difficulties are an essential component of the clinical picture of depression. Several interventional studies have demonstrated the value of specific insomnia treatment in the management of depression. Indeed, the absence of targeted treatment for insomnia increases the risk of depressive relapse. In this context, the importance of specific treatment of insomnia in cases of comorbidity with depression, and the need to integrate this approach into clinical practice, have recently been highlighted. However, very few studies have explored the efficacy of combined treatment of insomnia (with Cognitive Behavioural Therapy for Insomnia - CBT-I) and depression (with Behavioural Activation Treatment for Depression - BATD). However, one study has shown that BATD can have beneficial effects on sleep quality (in caregivers of people with Alzheimer's disease). The combined treatment of CBT-I and BATD, as well as the importance of the order of administration of these interventions in cases of insomnia-depression comorbidity, however, remain unexplored.

The aim of this study is to evaluate the overall effect of the combination of CBT-I and a BATD on depressive symptoms and insomnia in the short, medium and long term. It also seeks to examine the specific effects of each intervention. In addition, the study assesses efficacy and adherence under two different orders of treatment combination, while exploring the psychological mechanisms likely to promote positive symptoms change. Finally, it looks at inter-individual differences in responses to interventions. Our study will help provide empirical evidence on the efficacy of combined treatment for people suffering from insomnia and depression. By identifying the psychological mechanisms that may promote improvement in these comorbid disorders, it could also help refine and improve current treatments.

Participants will be recruited through a number of sources, including the CPLU (Clinique Psychologique et Logopédique de l Université de Liège), word of mouth, announcements within the University (e.g. via the student and staff quality of life service), social networks, and various CHU departments. A flyer will be distributed by clinicians and on social networks, including Facebook. Participants will also be identified through CHU psychologists, doctors and psychiatrists, who have potential access to the target population (people suffering from sleep disorders and depression).

An initial telephone interview will take place to check the inclusion and exclusion criteria, explain how the study works and the various appointment dates.

Participants wishing to take part in the study, but presenting exclusion criteria, will be redirected to appropriate care services according to their difficulties. This may include services specializing in sleep disorders, services dedicated to the management of psychological disorders, psychiatric emergencies in the event of significant suicidal ideation, or individual psychological follow-up by a specialized therapist (such as primary care psychologists or CBT psychotherapists).

If the person meets the criteria, an initial interview will be arranged. During this first clinical interview, the protocol will be presented in greater detail. Participants' expectations and motivations will be investigated to ensure that the proposed intervention can meet them. The information letter and informed consents will be offered to the participant. A socio-demographic questionnaire will be proposed. The content of the assessments to be completed daily will be presented to the participants. At the end of this interview, they will also be invited to complete the standardized pre-intervention questionnaires.

Participants will then begin self-observation for two weeks, before starting the first intervention (CBT-I in condition 1 and BATD in condition 2). This will be followed by a further two-week period of observation without intervention, prior to the second intervention (BATD in condition 1 and CBT-I in condition 2). A final two-week self-observation phase follows the second intervention.

Eligibility Criteria:
Inclusion Criteria:

* Participants will be adults with depression (PhQ 9 \&gt; 10; cut-off for moderate depression) and insomnia (Insomnia Severity Index \&gt; 11) who also meet DSM-V criteria for depression and insomnia (APA, 2013) and have a good understanding of French.

Exclusion Criteria:

* Participants requiring different treatment, i.e. those with symptoms suggestive of psychotic disorder, bipolar disorder, substance abuse disorder, excessive suicidal ideation, or other sleep pathology (such as sleep apnea, restless legs syndrome, narcolepsy, sleepwalking, or periodic limb movements)
* Participants who have recently received or are currently receiving other interventions that could be confused with our intervention, such as those undergoing treatment for sleep or depression, or those undergoing parallel psychological or pharmacological treatment (antidepressants and anxiolytics will be accepted provided they have been stabilized for at least two months and there are no planned changes in the following weeks).
* Participants with commitments that disrupt nocturnal sleep cycles and habits, such as those who no longer work or who work night shifts, will also be excluded from the study.