Cost-effective treatments are needed to reduce the burden of depression. One way to improve the cost-effectiveness of psychotherapy might be to increase session frequency, but keep the total number of sessions constant.

To evaluate the cost-effectiveness of twice-weekly compared with once-weekly psychotherapy sessions after 12 months, from a societal perspective.

An economic evaluation was conducted alongside a randomised controlled trial comparing twice-weekly versus once-weekly sessions of psychotherapy (cognitive–behavioural therapy or interpersonal psychotherapy) for depression. Missing data were handled by multiple imputation. Statistical uncertainty was estimated with bootstrapping and presented with cost-effectiveness acceptability curves.

Differences between the two groups in depressive symptoms, physical and social functioning, and quality-adjusted life-years (QALY) at 12-month follow-up were small and not statistically significant. Total societal costs in the twice-weekly session group were higher, albeit not statistically significantly so, than in the once-weekly session group (mean difference €2065, 95% CI −686 to 5146). The probability that twice-weekly sessions are cost-effective compared with once-weekly sessions was 0.40 at a ceiling ratio of €1000 per point improvement in Beck Depression Inventory-II score, 0.32 at a ceiling ratio of €50 000 per QALY gained, 0.23 at a ceiling ratio of €1000 per point improvement in physical functioning score and 0.62 at a ceiling ratio of €1000 per point improvement in social functioning score.

Based on the current results, twice-weekly sessions of psychotherapy for depression are not cost-effective over the long term compared with once-weekly sessions.

Despite growing concerns about mental health during the COVID-19 pandemic, particularly in people with pre-existing mental health disorders, research has shown that symptoms of depression and anxiety were generally quite stable, with modest changes in certain subgroups. However, individual differences in cumulative exposure to COVID-19 stressors have not been yet considered.

We aimed to quantify and investigate the impact of individual-level cumulative exposure to COVID-19-pandemic-related adversity on changes in depressive and anxiety symptoms and loneliness. In addition, we examined whether the impact differed among individuals with various levels of pre-pandemic chronicity of mental health disorders.

Between April 2020 and July 2021, 15 successive online questionnaires were distributed among three psychiatric case–control cohorts that started in the 2000s (N = 1377). Outcomes included depressive and anxiety symptoms and loneliness. We developed a COVID-19 Adversity Index (CAI) summarising up to 15 repeated measures of COVID-19-pandemic-related exposures (e.g. exposure to COVID-19 infection, negative economic impact and quarantine). We used linear mixed linear models to estimate the effects of COVID-19-related adversity on mental health and its interaction with pre-pandemic chronicity of mental health disorders and CAI.

Higher CAI scores were positively associated with higher increases in depressive symptoms, anxiety symptoms and loneliness. Associations were not statistically significantly different between groups with and without (chronic) pre-pandemic mental health disorders.

Individual differences in cumulative exposure to COVID-19-pandemic-related adversity are important predictors of mental health, but we found no evidence for higher vulnerability among people with (chronic) pre-pandemic mental health disorders.

Twice weekly sessions of cognitive behavioral therapy (CBT) and interpersonal psychotherapy (IPT) for major depressive disorder (MDD) lead to less drop-out and quicker and better response compared to once weekly sessions at posttreatment, but it is unclear whether these effects hold over the long run.

Compare the effects of twice weekly v. weekly sessions of CBT and IPT for depression up to 24 months since the start of treatment.

Using a 2 × 2 factorial design, this multicentre study randomized 200 adults with MDD to once or twice weekly sessions of CBT or IPT over 16–24 weeks, up to a maximum of 20 sessions. Main outcome measures were depression severity, measured with the Beck Depression Inventory-II and the Longitudinal Interval Follow-up Evaluation. Intention-to-treat analyses were conducted.

Compared with patients who received once weekly sessions, patients who received twice weekly sessions showed a significant decrease in depressive symptoms up through month 9, but this effect was no longer apparent at month 24. Patients who received CBT showed a significantly larger decrease in depressive symptoms up to month 24 compared to patients who received IPT, but the between-group effect size at month 24 was small. No differential effects between session frequencies or treatment modalities were found in response or relapse rates.

Although a higher session frequency leads to better outcomes in the acute phase of treatment, the difference in depression severity dissipated over time and there was no significant difference in relapse.

Mental health was only modestly affected in adults during the early months of the COVID-19 pandemic on the group level, but interpersonal variation was large.

We aim to investigate potential predictors of the differences in changes in mental health.

Data were aggregated from three Dutch ongoing prospective cohorts with similar methodology for data collection. We included participants with pre-pandemic data gathered during 2006–2016, and who completed online questionnaires at least once during lockdown in The Netherlands between 1 April and 15 May 2020. Sociodemographic, clinical (number of mental health disorders and personality factors) and COVID-19-related variables were analysed as predictors of relative changes in four mental health outcomes (depressive symptoms, anxiety and worry symptoms, and loneliness), using multivariate linear regression analyses.

We included 1517 participants with (n = 1181) and without (n = 336) mental health disorders. Mean age was 56.1 years (s.d. 13.2), and 64.3% were women. Higher neuroticism predicted increases in all four mental health outcomes, especially for worry (β = 0.172, P = 0.003). Living alone and female gender predicted increases in depressive symptoms and loneliness (β = 0.05–0.08), whereas quarantine and strict adherence with COVID-19 restrictions predicted increases in anxiety and worry symptoms (β = 0.07–0.11).Teleworking predicted a decrease in anxiety symptoms (β = −0.07) and higher age predicted a decrease in anxiety (β = −0.08) and worry symptoms (β = −0.10).

Our study showed neuroticism as a robust predictor of adverse changes in mental health, and identified additional sociodemographic and COVID-19-related predictors that explain longitudinal variability in mental health during the COVID-19 pandemic.

It is unclear what session frequency is most effective in cognitive–behavioural therapy (CBT) and interpersonal psychotherapy (IPT) for depression.

Compare the effects of once weekly and twice weekly sessions of CBT and IPT for depression.

We conducted a multicentre randomised trial from November 2014 through December 2017. We recruited 200 adults with depression across nine specialised mental health centres in the Netherlands. This study used a 2 × 2 factorial design, randomising patients to once or twice weekly sessions of CBT or IPT over 16–24 weeks, up to a maximum of 20 sessions. Main outcome measures were depression severity, measured with the Beck Depression Inventory-II at baseline, before session 1, and 2 weeks, 1, 2, 3, 4, 5 and 6 months after start of the intervention. Intention-to-treat analyses were conducted.

Compared with patients who received weekly sessions, patients who received twice weekly sessions showed a statistically significant decrease in depressive symptoms (estimated mean difference between weekly and twice weekly sessions at month 6: 3.85 points, difference in effect size d = 0.55), lower attrition rates (n = 16 compared with n = 32) and an increased rate of response (hazard ratio 1.48, 95% CI 1.00–2.18).

In clinical practice settings, delivery of twice weekly sessions of CBT and IPT for depression is a way to improve depression treatment outcomes.

The course of illness in obsessive–compulsive disorder (OCD) varies significantly between patients. Little is known about factors predicting a chronic course of illness. The aim of this study is to identify factors involved in inducing and in maintaining chronicity in OCD.

The present study is embedded within the Netherlands Obsessive Compulsive Disorder Association (NOCDA) study, an ongoing multicenter naturalistic cohort study designed to identify predictors of long-term course and outcome in OCD. For this study, 270 subjects with a current diagnosis of OCD were included. Chronicity status at 2-year follow-up was regressed on a selection of baseline predictors related to OCD, to comorbidity and to stress and support.

Psychotrauma [odds ratio (OR) 1.98, confidence interval (CI) 1.22–3.22, p = 0.006], recent negative life events (OR 1.42, CI 1.01–2.01, p = 0.043), and presence of a partner (OR 0.28, CI 0.09–0.85, p = 0.025) influenced the risk of becoming chronic. Longer illness duration (OR 1.46, CI 1.08–1.96, p = 0.013) and higher illness severity (OR 1.09, CI 1.03–1.16, p = 0.003) increased the risk of remaining chronic.

External influences increase the risk of becoming chronic, whereas the factors involved in maintaining chronicity are illness-related. As the latter are potentially difficult to modify, treatment should be devoted to prevent chronicity from occurring in the first place. Therapeutic strategies aimed at alleviating stress and at boosting social support might aid in achieving this goal.

Mindfulness-based cognitive therapy (MBCT) and maintenance antidepressant medication (mADM) both reduce the risk of relapse in recurrent depression, but their combination has not been studied.

To investigate whether MBCT with discontinuation of mADM is non-inferior to MBCT+mADM.

A multicentre randomised controlled non-inferiority trial (ClinicalTrials.gov: NCT00928980). Adults with recurrent depression in remission, using mADM for 6 months or longer (n = 249), were randomly allocated to either discontinue (n = 128) or continue (n = 121) mADM after MBCT. The primary outcome was depressive relapse/recurrence within 15 months. A confidence interval approach with a margin of 25% was used to test non-inferiority. Key secondary outcomes were time to relapse/recurrence and depression severity.

The difference in relapse/recurrence rates exceeded the non-inferiority margin and time to relapse/recurrence was significantly shorter after discontinuation of mADM. There were only minor differences in depression severity.

Our findings suggest an increased risk of relapse/recurrence in patients withdrawing from mADM after MBCT.

Anxiety disorders increase the risk of onset of several ageing-related somatic conditions, which might be the consequence of accelerated cellular ageing.

To examine the association between anxiety status and leukocyte telomere length (LTL) as an indicator of cellular ageing.

Data are from individuals with current (n = 1283) and remitted (n = 459) anxiety disorder, and controls (n = 582) with no psychiatric disorder from the Netherlands Study of Depression and Anxiety. We determined DSM-IV anxiety diagnoses and clinical characteristics by structured psychiatric interviews and self-report questionnaires; LTL was assessed using quantitative polymerase chain reaction and converted into base pairs (bp).

Patients in the current anxiety group (bp = 5431) had significantly shorter LTL compared with the control group (bp = 5506, P = 0.01) and the remitted anxiety group (bp = 5499, P = 0.03) in analyses adjusted for sociodemographics, health and lifestyle. The remitted anxiety group did not differ from the control group (P = 0.84), however, time since remission was positively related with LTL. Furthermore, anxiety severity scores were associated with LTL in the whole sample, in line with a dose–response association.

Patients with current – but not remitted – anxiety disorder had shorter telomere length, suggesting a process of accelerated cellular ageing, which in part may be reversible after remission.

There is an urgent need for the development of cost-effective preventive strategies to reduce the onset of mental disorders.

To establish the cost-effectiveness of a stepped care preventive intervention for depression and anxiety disorders in older people at high risk of these conditions, compared with routine primary care.

An economic evaluation was conducted alongside a pragmatic randomised controlled trial (ISRCTN26474556). Consenting individuals presenting with subthreshold levels of depressive or anxiety symptoms were randomly assigned to a preventive stepped care programme (n = 86) or to routine primary care (n = 84).

The intervention was successful in halving the incidence rate of depression and anxiety at €563 (£412) per recipient and €4367 (£3196) per disorder-free year gained, compared with routine primary care. The latter would represent good value for money if the willingness to pay for a disorder-free year is at least €5000.

The prevention programme generated depression- and anxiety-free survival years in the older population at affordable cost.