Psychometric conceptualizations of psychopathology have gained popularity. Most prominent approaches are the common factor (CF) and the symptom network models. A known problem in theory development through empirical findings is the statistical indistinguishability of CF and symptom network models in cross-sectional data. However, the extent of this problem and its implications have not been inspected formally for longitudinal studies. In this study, we sought to clarify the distinguishability between CF and symptom network models in longitudinal designs. We show necessary and sufficient conditions for indistinguishability in covariance for commonly applied vector autoregressive symptom network models and CF models and suggest a procedure for assessing whether a CF model can be refuted based on an estimated symptom network model. We give easy-to-implement R -functions for conducting the comparison. Numerical and empirical examples show that potential indistinguishability is relevant when interpreting the published literature. Overall, this study promotes comparative analysis of symptom network and CF models.

BACKGROUND:Depression and anxiety are among the most prevalent mental health problems globally, with psychotherapy serving as a first-line treatment. Initial symptom severity, prior treatment history, waiting time, and session frequency may influence treatment effectiveness in routine care. METHODS:We analyzed session-by-session data from clients receiving a seven-session cognitive-behavioral therapy (CBT) program for depression (N = 2627) or anxiety (N = 3929) in primary care. Symptoms were assessed using the PHQ-9 and GAD-7 at each session. The magnitude and rate of change were examined using pre-post comparisons and linear mixed models. RESULTS:Clients showed significant reductions in both depressive (mean change -4.45 PHQ-9 points, 95% CI -4.69, -4.22) and anxiety symptoms (mean change -4.36 GAD-7 points, 95% CI -4.54, -4.17). Higher initial symptom severity was associated with faster reductions, while prior psychiatric care or previous very long-term psychotherapy were associated with smaller pre-post gains. Waiting time and session frequency were not consistently related to outcomes. CONCLUSIONS:In routine CBT, clients with higher baseline severity benefited substantially, supporting equitable access to CBT regardless of initial symptom level. Clinical improvement was driven by the total number of attended treatment sessions rather than by the rate of attendance (i.e., the number of sessions per unit of time). This supports flexible scheduling without compromising outcomes. Longer waiting times did not systematically predict poorer results, suggesting that client- versus system-driven delays may have distinct implications. Considering prior treatment history may help tailor interventions for individuals with more persistent or treatment-resistant symptom patterns.

PURPOSE:COVID-19 challenged health care personnel from spring 2020 to the introduction of vaccines. This prospective cohort study evaluated the psychological impact of cumulated exposure to COVID-19 frontline work and COVID-19-related potentially traumatic events (PTEs) on all hospital personnel. MATERIALS AND METHODS:PTEs, posttraumatic stress disorder (PTSD) symptoms, psychological distress, insomnia, anxiety and depression symptoms were assessed with screening tools monthly during the first year and later bimonthly in this study among HUS Helsinki University Hospital personnel who participated in this study. The initial number of participants was N = 4910 (19% of the hospital personnel), 85% of whom reparticipated in some of the 16 follow ups and N = 1128 at 24 months (last follow up). RESULTS:The most important PTE before PTSD symptoms was strong anxiety due to fear of one's own or a close one's infection (odds ratio, OR 2.39, 95% confidence interval, CI 1.92-2.98), followed by exceptionally disturbing or distressing pandemic work assignments (OR 1.69, 95% CI 1.41-2.02). Frontline work and direct exposure to pandemic patients alone did not statistically significantly increase PTSD risk (OR 1.05, 95% CI 0.89-1.23). Accumulation of PTEs (OR 1.07 per PTE, 95% CI 1.03-1.12) and prolonged frontline work (OR 1.05, 95% CI 1.01-1.10) over time were risk factors for psychological distress. CONCLUSIONS:Accumulated exposures to PTEs and frontline work constitute an additional risk of distress and stress-related disorders. The subjective nature of the most prominent risk, PTE (fear of infections), suggests that workplace interventions and emotional support might prevent distress during a pandemic.

Symptoms of depression and anxiety frequently co-occur, but traditional discrete-time models fail to capture their causal interactions. To explore the dynamic relationship between these symptoms, we applied two advanced methodologies—non-Gaussian direction of dependence analyses and continuous-time structural equation modeling—across two therapist-guided internet-based cognitive-behavioral therapy (iCBT) samples and two general-population cohorts ( N = 22,530). Our findings revealed that in iCBT, neither depression nor anxiety exhibited causal dominance; instead, changes were driven by shared transdiagnostic processes. In the general population, depression showed unidirectional causal dominance over anxiety; stable symptom levels were sustained by shared time-invariant factors over multiple years. Overall, this large-scale study suggests that the interplay between depression and anxiety is primarily driven by shared transdiagnostic processes alongside the causal primacy of depression. These insights underscore the importance of non-Gaussian and continuous-time modeling in understanding mental-health comorbidities and advocate for transdiagnostic practices in treating both depression and anxiety.

Background Identifying the principal and comorbid diagnoses of a patient suffering from a major depressive episode (MDE) is crucial. Ecological momentary assessment (EMA) may help identify patterns of symptom fluctuations characteristic of a specific disorder and thus potentially improve the differential diagnostics. Methods This EMA study aimed to investigate the real-time group differences in temporal variations of depressive symptoms in patients with an ongoing MDE and a diagnosis of bipolar (BD; n = 17), borderline personality (BPD; n = 15), or major depressive disorder (MDD; n = 45) and healthy controls (HC; n = 23). Multilevel modeling analyses were performed to assess the mean level, inertia, and variability of five symptom dimensions, all ranging from positive to negative: mood, anger, anhedonia, energy, and hopelessness. Results All patient groups showed significantly different mean levels of all symptoms compared with HC as well as significantly greater inertia of anger and anhedonia. Furthermore, BPD patients exhibited significantly greater inertia of mood, anhedonia, and hopelessness than BD and MDD groups. By modeling different variance structures, variability of all five symptoms was found to be lowest among HC and highest among BD and/or BPD groups. Energy was the only symptom dimension where the difference in variability could also be found in the BD-BPD group comparison. Limitations While the overall number of participants included (n = 100) was moderate for an EMA study, numbers of patients in the BD and BPD subgroups were small. Conclusions These findings suggest partially different temporal variations of depressive symptoms among depressed patients with BD, BPD, or MDD and HC.

Background: Major depressive episodes (MDEs) are phenomenologically heterogeneous. The Multidimensional Assessment of Thymic States (MAThyS) scale was developed to estimate activation/inhibition, emotional reactivity, and to differentiate types of depression in bipolar disorder (BD). Their role in diagnosis or other depressions remains unclear. Methods: We assessed validity of Finnish translation of the MAThyS in 94 patients with Major Depressive Disorder (MDD), MDE/BD, or MDE/BPD (MDE comorbid with Borderline Personality Disorder), and 29 healthy controls. We examined the associations of MAThyS total score with depression severity (MADRS), (hypo)manic symptoms (YMRS, MIXMDE), and BPD severity (BPDSI), assessed internal consistency, and conducted confirmatory factor analysis to test the postulated two-factor structure. Results: MAThyS demonstrated good internal consistency in patient subcohorts (Cronbach’s α = 0.78–0.88), but not in controls (α = 0.19). In hierarchical regression model (adjusted R² = 0.34), MAThyS total score was negatively associated with depression severity (MADRS) (β = –0.316, p = 0.003), but positively with mixed symptoms (MIXMDE; β = 0.319, p = 0.017), borderline severity (BPDSI; β = 0.195, p = 0.13) and momentary (hypo)manic symptoms (YMRS; β = 0.171, p = 0.15). The two-factor model had poor fit (CFI = 0.687; RMSEA = 0.125). Conclusions: The Finnish MAThyS translation retains good internal consistency, for total scores assessed in MDE patient subgroups, but validity of the scale in assessing activation and emotional reactivity specifically remains unclear. MAThyS may aid in detecting signs of increased activation and mixed features. Further studies are needed to evaluate its validity and clinical utility.

Background According to meta-analyses of randomised controlled trials (RCTs), therapist-guided internet-delivered cognitive behavioural therapy (iCBT) is as effective a treatment for depression as traditional face-to-face CBT (fCBT), despite its substantially lower costs. However, RCTs are not always representative of routine practice, which could inflate effectiveness estimates. We combined rich data with counterfactual causal statistical reasoning to provide an fCBT-iCBT comparison complementary to RCTs. Methods In this retrospective cohort study, we linked full archived therapist-guided iCBT and fCBT cohort registries with multiple Finnish social and health care registries. The therapist-guided iCBT programme with third-wave principles and the fCBTs were provided by HUS Helsinki University Hospital to people with depression without acute suicide or substance-misuse risk; fCBT was delivered in the Uusimaa region, whereas therapist-guided iCBT was nationwide and excluded people with treatment-interfering psychotic, neurological, or personality disorders, chronic or bipolar depression, or aged under 16 years. The primary outcome was the causal average treatment effect (ATE) for the difference in during-treatment symptom reductions between fCBT and therapist-guided iCBT, with symptoms measured by the Patient Health Questionnaire-9 (PHQ-9). If only one PHQ-9 report was recorded, no change was recorded, thereby penalising dropout. For an optimal and robust (a posteriori-balanced) ATE estimate, we applied targeted maximum likelihood machine learning. There was no involvement of individuals with lived experience in the research and writing process. Findings The guided iCBT registry recorded patients from Dec 12, 2018, to Dec 22, 2022, and the fCBT registry spanned Aug 28, 2018, to Sept 28, 2022. From the total of 32 343 registered therapies, 392 people were included from the fCBT registry and 5467 people from the iCBT registry. Four people in the fCBT group and 21 in the guided iCBT group had missing baseline data, therefore the main sample for analysis contained 5834 patients (4101 [70%] were female and 1733 [30%] were male) with a mean age of 35 years (SD 12). Altogether, 5455 (94%) patients were registered with Finnish as their native language. The ATE estimate indicated that the PHQ-9 score declined 0745 points (95% CI 0156-1334) more in the iCBT group than in the fCBT group. Sensitivity analyses concurred. Interpretation Considered alongside previous RCTs, our findings suggest that short first-line treatments with therapist-guided iCBT are at least as effective and efficacious as fCBT. Our findings eliminate error sources and extend the representativeness of the population for this cost-effective treatment. Funding The Research Council of Finland (Academy of Finland).

Psychological pain (PP) is a potentially important risk factor for suicide. However, its temporal stability and association with suicidal ideation (SI) remain obscure. Whether PP represents a risk factor for SI independently of depression, anxiety, and hopelessness or is more prominent and temporally unstable in patients with depression and borderline personality disorder (BPD) is also unclear.

Background:Complementing the development of evidence-based psychological therapies, practice-based evidence has developed from patient samples collected in routine care, addressing questions relevant to patients and practitioners, and thereby expanding our knowledge of psychological therapies and their impact. Implementation of assessments in routine care allows for timely clinical decision support and the collection of multiple practice-based data sets by addressing the needs of patients and clinicians (e.g., routine outcome monitoring) and the needs of researchers (e.g., identifying the impact of therapist variables on outcomes). Method:In this article we describe an initiative developed in Europe, through the European Chapter of the Society for Psychotherapy Research, aimed at creating a consortium that has the potential for collecting data on tens of thousands of patients per year. Results:A survey identified one of the main problems in the development of a common data set to be the heterogeneity of measures used by members (e.g., 87 different pre-post outcomes). We report on the results of the survey and the initial stage of identifying a single-item - the Emotional and Psychological Outcome (EPO-1) - measure and the process of its translation into multiple European languages. Conclusions:We conclude this first stage of the overall project by discussing the future potential of the Consortium in relation to the development of procedures that allow crosswalks of outcome measures and the creation of a task force that may be consulted when new data sets are collected, aiming for new common measures to be implemented and shared.

Objective: Psychological pain (PP) is a potentially important risk factor for suicide. However, its temporal stability and association with suicidal ideation (SI) remain obscure. Whether PP represents a risk factor for SI independently of depression, anxiety, and hopelessness or is more prominent and temporally unstable in patients with depression and borderline personality disorder (BPD) is also unclear. Methods: From November 2020 to December 2022, psychiatric inpatients with depression without (N = 37) and with (N =30) BPD were recruited to an ecological momentary assessment (EMA) study, wherein their PP, severity of depression, SI, and hopelessness were assessed 3 times daily using visual analog scales. Multilevel regression models were estimated. Results: Altogether, 4,320 EMA observations were collected. PP correlated with hopelessness (r= 0.417), depression (r= 0.339), and anxiety (r= 0.496), but the between-patient variance of PP remained at 1.26 (95% CI, 1.025-1 .533) after controlling for these variables. The within-patient variance of PP was associated with SI ((3 = 0.17 [95% CI, 0.12-0.22]) with a magnitude comparable to hopelessness ((3= 0.1 [95% CI, 0.05-0.1 5]) and depression ((3= 0.12 [95% CI, 0.08-0.1 7]). Patients with depression and BPD reported higher daily PP and SI (P< .001) and a more prominent within-patient variation in PP. Conclusions: In psychiatric inpatients with depression, besides depression and hopelessness, PP represents an independent risk factor for SI, varying within a timescale of days. Depressive patients with BPD may experience more prominent and temporally unstable PP, likely underlying their higher vulnerability to SI.

Unlike depression sum scores, the underlying risk for depression is typically assumed to be normally distributed across the general population. To assess the true empirical shape of depression risk, we created a continuous-valued estimate of the latent depression density, using the Davidian-Curve Item Response Theory (DC-IRT) and the National Health and Nutrition Examination Survey (NHANES) cohorts from 2005 to 2018 ( n = 36,244 on the Nine-item Patient Health Questionnaire; PHQ-9). We conducted simulations to investigate the performance of DC-IRT for large samples and realistic items. The method can recover complex latent-risk distributions even when they are not evident from sum scores. However, estimation accuracy for different sample sizes depends on the method of model selection. In addition to full-data analysis, random samples of a few thousand observations were drawn for analysis. The latent shape of depression was left-skewed and bimodal in both investigations, indicating that the latent-normality assumption does not hold for depression.

Objective: Psychological pain (PP) is a potentially important risk factor for suicide. However, its temporal stability and association with suicidal ideation (SI) remain obscure. Whether PP represents a risk factor for SI independently of depression, anxiety, and hopelessness or is more prominent and temporally unstable in patients with depression and borderline personality disorder (BPD) is also unclear. Methods: From November 2020 to December 2022, psychiatric inpatients with depression without (N = 37) and with (N = 30) BPD were recruited to an ecological momentary assessment (EMA) study, wherein their PP, severity of depression, SI, and hopelessness were assessed 3 times daily using visual analog scales. Multilevel regression models were estimated. Results: Altogether, 4,320 EMA observations were collected. PP correlated with hopelessness (r= 0.417), depression (r= 0.339), and anxiety (r= 0.496), but the between-patient variance of PP remained at 1.26 (95% CI, 1.025-1.533) after controlling for these variables. The within-patient variance of PP was associated with SI (beta = 0.17 [95% CI, 0.12-0.22]) with a magnitude comparable to hopelessness (beta = 0.1 [95% CI, 0.05-0.15]) and depression (beta = 0.12 [95% CI, 0.08-0.17]). Patients with depression and BPD reported higher daily PP and SI (P< .001) and a more prominent within-patient variation in PP. Conclusions: In psychiatric inpatients with depression, besides depression and hopelessness, PP represents an independent risk factor for SI, varying within a timescale of days. Depressive patients with BPD may experience more prominent and temporally unstable PP, likely underlying their higher vulnerability to SI.

Introduction: Patients with depression often require inpatient treatment due to their high suicide risk. Ecological momentary assessment (EMA) studies have shown that suicidal ideation (SI) fluctuates over time. As affective instability and psychological pain (PP) are common experiences in borderline personality disorder (BPD), often comorbid with depression, we examined factors predicting short-term changes of SI in depressive inpatients with or without BPD. Methods: Psychiatric inpatients with depression with (N = 30) or without (N = 37) comorbid BPD assessed their anxiety, PP, severity of depression, SI, and hopelessness three times daily using visual analogue scales. Multilevel regression models were estimated. Results: Altogether 4320 EMA observations, spanning on average 3.4 successive days, were collected. Only severity of depression (8 = 0.19; [95 % CI = 0.06, 0.32]) and previous SI (8 = 0.32; [95 % CI = 0.23, 0.41]) predicted near-future SI within several hours. PP predicted near-future SI in inpatients with depression and BPD (8 = 0.28; [95 % CI = 0.11, 0.46]), but not in patients without BPD. Limitations: The follow-up data represents only the first days of hospitalization. The context of the EMA is the acute psychiatric ward, affecting generalizability to outpatients. Conclusions: Short-terms changes in SI are predicted by changes in severity of depression and previous SI in depressed inpatients without BPD, and also by changes in PP in depressed inpatients with BPD. As SI and its risk factors may oscillate within a time scale of hours, frequent monitoring of momentary severity of depression, PP, and SI may be warranted in inpatient settings.

Differentiating major depressive episodes (MDEs) of major depressive disorder (MDD), bipolar disorder (MDE/BD) and the MDEs comorbid with borderline personality disorder (MDE/BPD) is crucial for appropriate treatment, and knowledge of phenomenological differences may aid this. However, studies comparing affect experiences of these three patient groups and healthy subjects are scarce. In our study, participants (N = 114), including patients with MDD (n = 34), MDE/BD (n = 27), and MDE/BPD (n = 24), and healthy controls (HC, n = 29) responded to ecological momentary assessment (EMA) with ten circumplex model affect items ten times daily for seven days (7709 recordings). Explorative factor analysis resulted in two affect dimensions. The positive dimension included active, excited, cheerful (high arousal), and content (low arousal) affects, and the negative dimension irritated, angry, and nervous (high arousal) affects. Relative to HC, patients reported 3.5-fold negative affects (mean MDD 1.36 (SD 0.92), MDE/BD 1.43 (0.76), MDE/BPD 1.81 (0.95) vs. HC 0.44 (0.49) (p < 0.01)) but 0.5-fold positive affects (2.01 (0.90), 1.95 (0.89), 2.24 (1.03), vs. 3.2 (0.95), respectively (p < 0.01)). We used multilevel modelling. Negative-affect within-individual stability was lowest in MDE/BPD and highest in MDD. Negative affect predicted concurrent positive affect more in MDE/BPD than in MDD. Moderate size of subcohorts and no inpatients were limitations. Despite apparently similar MDEs, affective experiences may differ between BPD, BD, and MDD patients. Clinical subgroups of patients with depression may vary in affective instability and concurrent presence of negative and positive affects during depression.

Being physically inactive can worsen mental health. Physical inactivity and depression are associated, but the temporal precedence and underlying mechanism are unclear; symptoms affecting future physical activity may not be the same symptoms as those associated with and affected by it. We used large European cohort (Survey of Health, Ageing, and Retirement in Europe, SHARE, N= 124, 526) to study temporal associations between physical inactivity and individual depressive symptoms. Multivariate regression with robust standard errors were used to analyze how physical inactivity is associated with later depression and how depressive symptoms predict later physical inactivity. After adjusting the models for demographics, other health behaviors, BMI, and chronic diseases, physical inactivity was prospectively associated with 10 of the 12 depressive symptoms and 7 of the 12 baseline depressive symptoms were prospectively associated with physical inactivity. These findings were robust for adjusting for antidepressant medication. Age-stratified analyses suggested that the associations between physical inactivity and depressive symptoms were independent of age. Omitting the most influential symptom, lack of enjoyment, from the sum score attenuated the association by 13% in the longitudinal and by 26% in the cross-sectional analyses. These findings suggest that physical inactivity and depression are bidirectionally associated even at symptom-level.

ObjectiveBehavioral activation (BA) is an effective treatment for depression. We investigated the effectiveness of add-on group-format BA and peer support (PS) with treatment as usual (TAU) in a registered randomized clinical trial in psychiatric outpatient settings (ISRCTN10647845).MethodsAdult outpatients (N = 140) with major depressive disorder (MDD) and Patient Health Questionnaire (PHQ-9) score ≥10 were randomized into a) group BA, consisting of eight 90-minute weekly group sessions plus TAU; b) group PS, including eight 90-minute weekly group sessions plus TAU; or c) TAU alone. The primary outcome was a within-individual change in PHQ-9 score between baseline and 8 weeks. Secondary outcomes were 1) response, 2) remission, and 3) functional impairment at 8 weeks, plus 4) change in PHQ-9 at 6 months.ResultsOf the randomized patients, 100 (71.4%) completed treatments, including 29/45 (64.4%) patients in the BA group, 39/49 (79.6%) in the PS group, and 32/46 (69.6%) in the TAU group. By 8 weeks, PHQ-9 scores declined most in the TAU group [BA −0.28 (95% CI −2.48, 1.92), PS −0.58 (−2.09, 0.94) vs. TAU −3.32 (−5.21, −1.44); group-difference test, p = 0.034]. The secondary outcomes in the BA or PS arms did not significantly differ from those in TAU. Videotaped sessions revealed marked variation in briefly trained therapists’ adherence to the treatment manual.ConclusionsIn this randomized trial, the effectiveness of treatments with the added BA and PS groups did not exceed that of TAU alone. The preconditions in which brief BA or PS group interventions benefit outpatients with depression in psychiatric settings warrant critical investigation.

Background: Internet-delivered cognitive behavioral therapy (iCBT) is effective in the treatment of anxiety disorders. iCBT clinical trials use relatively long and time-consuming disorder-specific rather than transdiagnostic anxiety measurements. Overall Anxiety Severity and Impairment Scale (OASIS) is a brief self-report scale that could offer a universal, easy-to-use anxiety measurement option in disorder-specific and transdiagnostic iCBT programs. Objective: We aimed to investigate relationships between OASIS and disorder-specific instruments in iCBT. We expected these relationships to be positive. Methods: We investigated patients in original nationwide iCBT programs for generalized anxiety disorder (GAD), obsessive-compulsive disorder, panic disorder, and social anxiety disorder, which were administered by Helsinki University Hospital, Finland. In each program, anxiety symptoms were measured using both disorder-specific scales (the 7-item Generalized Anxiety Disorder scale, Penn State Worry Questionnaire, revised Obsessive-Compulsive Inventory, Panic Disorder Severity Scale, and Social Phobia Inventory) and by OASIS. A general linear model for repeated measures (mixed models) and interaction analysis were used for investigating the changes and relationships in the mean scores of OASIS and disorder-specific scales from the first session to the last one. Results: The main effect of linear mixed models indicated a distinct positive association between OASIS and disorder-specific scale scores. Interaction analysis demonstrated relatively stable associations between OASIS and the revised Obsessive-Compulsive Inventory (F-822.9=0.09; 95% CI 0.090-0.277; P=.32), and OASIS and the Panic Disorder Severity Scale (F-596.6=-0.02; 95% CI -0.108 to -0.065; P=.63) from first the session to the last one, while the 7-item Generalized Anxiety Disorder scale (F-4345.8=-0.06; 95% CI -0.109 to -0.017; P=.007), Penn State Worry Questionnaire (F-4270.8=-0.52; 95% CI -0.620 to -0.437; P<.001), and Social Phobia Inventory (F-862.1=-0.39; 95% CI -0.596 to -0.187; P<.001) interrelated with OASIS more strongly at the last session than at the first one. Conclusions: OASIS demonstrates clear and relatively stable associations with disorder-specific symptom measures. Thus, OASIS might serve as an outcome measurement instrument for disorder-specific and plausibly transdiagnostic iCBT programs for anxiety disorders in regular clinical practice.

Background: Psychotherapy for depression aims to reduce symptoms and to improve psychosocial functioning. We examined whether some symptoms are more important than others in the association between depression and functioning over the course of psychotherapy treatment.Methods: We studied associations between specific symptoms of depression (PHQ-9) and change in social and occupational functioning (SOFAS), both with structural equation models (considering liabilities of depression and each specific symptom) and with logistic regression models (considering the risk for individual patients). The study sample consisted of adult patients (n symbolscript 771) from the Finnish Psychotherapy Quality Registry (FPQR) who completed psychotherapy treatment between September 2018 and September 2021.Results: Based on our results of logistic regression analyses and SEM models, the baseline measures of depression symptoms were not associated with changes in functioning. Changes in depressed mood or hopelessness, problems with sleep, feeling tired, and feeling little interest or pleasure were associated with improved func-tioning during psychotherapy. The strongest evidence for symptom-specific effects was found for the symptom of depressed mood or hopelessness. Limitations: Due to our naturalistic study design containing only two measurement points, we were unable to study the causal relationship between symptoms and functioning. Conclusions: Changes in certain symptoms during psychotherapy may affect functioning independently of un-derlying depression. Knowledge about the dynamics between symptoms and functioning could be used in treatment planning or implementation. Depressed mood or hopelessness appears to have a role in the dynamic relationship between depression and functioning.

Assessment of treatment response in psychotherapies can be undermined by lack of longitudinal measurement invariance (LMI) in symptom self-report inventories, by measurement error, and/or by wrong model assumptions. To understand and compare these threats to validity of outcome assessment in psychotherapy research, we studied LMI, sum scores, and Davidian Curve Item Response Theory models in a naturalistic guided internet psychotherapy treatment register of 2,218 generalized anxiety disorder (GAD) patients and 3,922 depressive disorder (DD) patients (aged ≥16 years). Symptoms were repeatedly assessed by Generalized Anxiety Disorder Assessment-7 (GAD-7) or Beck Depression Inventory. The symptom self-reports adhered to LMI under equivalence testing, suggesting sum scores are reasonable proxies for disorder status. However, the standard LMI assumption of normally distributed latent factors did not hold and inflated treatment response estimates by 0.2 to 0.3 standard deviation units compared with sum scores. Further methodological research on non-normally distributed latent constructs holds promise in advancing LMI and mental health assessment.

Background: The association between physical activity (PA) and depression is well-established, but the details that explain this association remain elusive. We examined whether PA is differentially associated with specific symptoms of depression (e.g., cognitive vs somatic symptoms), and whether these associations follow a dose-response pattern with respect to intensity or frequency of PA. Methods: Cross-sectional analyses were based on 6 samples of the continuous U.S. National Health and Nutrition Examination Surveys (NHANES) carried out between 2007 and 2018 (n = 28,520). Depressive symptoms were assessed with Patient Health Questionnaire 9 (PHQ-9). Information about PA (vigorous, moderate, and daily commuting by foot or bike) and covariates was self-reported.Results: After adjusting for education, health behaviors, body-mass index, physical functioning, and all the other depressive symptoms, lower PA was specifically associated with four depressive symptoms: loss of interest/ pleasure, feeling down/hopeless, fatigue, and changes in appetite (odds ratios from 0.94 to 0.59). A monotonic dose-response pattern on PA amount was observed only for interest/pleasure and fatigue, and these associations were independent of PA intensity.Limitations: Cross-sectional data did not allow us to assess temporal ordering. Both depressive symptoms and PA were self-reported, which may induce bias.Conclusion: Low PA may be linked to depressive symptoms particularly through the symptoms of anhedonia and fatigue. Given that their association with PA amount follows a dose-response pattern and is independent of PA intensity, we hypothesize that behavioral activation and exposure to rewarding experiences might help to explain why PA alleviates depression.