The primary objective is to evaluate the (cost-)effectiveness of exposure therapy (ET) delivered by trained mental health nurses (MHNs) in terms of anxiety symptoms and quality of life for late life anxiety disorders in primary care compared to usual care (UC).

UC is not restricted, and the general practitioner (GP) is encouraged to work according to the guidelines of the Dutch College of GPs.

Participants in the ET group will receive 30-minute ET sessions delivered by a trained mental health nurse, during 8 sessions within the span of 12 weeks. Participants will fill in questionnaires before, during and after treatment, with a 1-year follow-up. The main study parameters are anxiety severity, quality of life and societal costs.

Rationale: Anxiety disorders are common and have a high disease burden throughout the life span. Nonetheless, older people with anxiety disorders remain undiagnosed and thus undertreated. Ageism, changes in symptom phenomenology at older age and transportation barriers are reasons for underdiagnosis/-treatment. Moreover, when treated, older patients generally receive pharmacotherapy, while adverse effects increase with age and 75% of older persons prefer psychotherapy. The most effective psychotherapy, i.e. exposure therapy, has not yet been evaluated for older adults with anxiety in primary care.

Exposure Therapy (ET) is the most effective intervention for all anxiety disorders in adults. It has the potential to reduce the risk of chronicity, inappropriate healthcare use, inappropriate drug use, and unnecessary referral to specialist mental healthcare providers, which often include long, costly treatment trajectories. Exposure is well-suited to be delivered by mental health nurses (MHNs; or POH-GGZ (praktijkondersteuner geestelijke gezondheidszorg) in Dutch) in primary care centers (PCCs) because older people visit their general practitioner (GP) regularly, and PCCs in the Netherlands have the availability of MHNs. However, they are currently not equipped to offer exposure. Introducing MHN-led exposure is likely to be (cost-)effective as it matches patients' preferences and prevents inadequate or costly treatments.

Objective: The primary objective is to evaluate the (cost-)effectiveness of ET delivered by trained MHNs regarding anxiety symptoms and quality of life for late-life anxiety disorders in primary care compared to Usual Care (UC). UC is not restricted, and the GP is encouraged to work according to the guidelines of the Dutch College of GPs.

Study design: A multi-center cluster-randomized controlled trial (RCT) with two parallel groups: a) ET and b) UC, in PCCs with a 1-year follow-up.

Study population: 170 patients, 65 years and older, with an anxiety disorder according to Diagnostic and Statistical Manual of Mental Disorders (DSM-5).

Intervention (if applicable): During 8 sessions within the span of 12 weeks, 30-minute ET sessions are delivered by a trained mental health nurse.

Main study parameters/endpoints: Anxiety severity as assessed with the Geriatric Anxiety Inventory (GAI), societal costs with the Trimbos and iMTA(Institute for Medical Technology Assessment) questionnaire on Costs associated with Psychiatric illness (TIC-P) and quality of life using the EuroQol 5 Dimension 5 Level version (EQ-5D-5L) during the 12-week treatment period and 1-year follow-up.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Though the burden includes investment of the patient, no risks are associated with participation in the study. By offering participants ET in the PCC by the MHN, the participants will benefit immediately as we expect a positive influence on their anxiety symptoms.

Inclusion Criteria:

• A primary DSM-5 anxiety disorder using the Mini Internationaal Neuropsychiatrisch Interview (MINI).
• One of the following DSM-5 anxiety disorders will be diagnosed, Generalized Anxiety Disorder, Agoraphobia, Panic Disorder or Social Anxiety Disorder.
• Participants are required to be sufficient in Dutch.

Exclusion Criteria:

• Exclusion criteria include somatic and/or another psychiatric morbidity that could interfere with diagnosing or treatment.
• Moderate to severe suicidality, which will be determined using the MINI
• Chronic and interfering substance or alcohol abuse
• Having received previous psychotherapy including exposure in the past year. -
• Antidepressants and benzodiazepines use are allowed if on a stable dose for a minimum of 8 weeks.
• Participants will be excluded if they score lower than 18 points on the MoCa (115). A score of <18 is indicative for moderate to severe cognitive impairment. - Participants will be excluded if they are terminally ill.

First assessments will be applied by project researchers and the following assessments will be applied by independent research assistants who are blinded for the condition.