This was a parallel, 2-group RCT with a 1:1 allocation ratio, in which individual participants were randomized to test the superiority of DadBooster over a waitlist control for fathers with diagnosed depression. The primary outcomes were severity of symptoms of depression and remission from the depressive episode at 12 weeks after enrollment. The trial was prospectively registered with the Australian and New Zealand Clinical Trials Registry on July 22, 2022 (ACTRN12622001029785). The first participant was enrolled on August 30, 2022; recruitment continued until July 2024. A single deviation from the registered protocol is described in the Statistical Methods section. In addition, a clarification regarding blinding procedures is provided in the Blinding section, as the trial registration did not fully capture assessor and analyst blinding. The trial is reported in accordance with the CONSORT (Consolidated Standards of Reporting Trials) 2025 statement and the CONSORT-eHEALTH (Consolidated Standards of Reporting Trials of Electronic and Mobile Health Applications and Online Telehealth) guidelines for web-based and mobile health interventions (Checklists 1 and 2) [33,34].

The trial was conducted in Australia, with participants recruited nationally across rural and metropolitan areas. Participants were recruited directly from the community via online methods, as well as through referral pathways from health professionals and services. All study procedures and intervention delivery were conducted remotely (primarily online with additional telephone contact) by the Parent-Infant Research Institute. The trial was a single-site study.

Marketing focused on social media campaigns, as well as promotion to health professionals and services (eg, maternal and child health nurses, early parenting centers, and perinatal mental health services) via information sessions, newsletter articles, and conference displays. Health professionals were encouraged to refer their clients to the project. Interested individuals followed links or QR codes from posters, postcards, or social media to obtain further information and to begin the screening process by visiting the secure project recruitment website. Informed consent was obtained from all trial participants.

Inclusion criteria were (1) fathers aged 18 years and older, (2) infants aged less than 1 year, (3) Australian residency, (4) English speaking, (5) no current treatment for depression (medication or therapy) to ensure effects could be attributed to the DadBooster intervention, (6) presence of depressive symptoms based on the Patient Health Questionnaire-9 (PHQ-9 ≥9) [35], and (7) diagnosis of current major depressive disorder or depressive disorder with insufficient symptoms.

Exclusion criteria were (1) Post-Traumatic Stress Disorder using the Primary Care PTSD screen for DSM-5 [36], (2) psychotic symptoms using the DSM-5 Self-Rated Level 1 Cross-Cutting Symptom Measure—Adult Psychosis domain [37], (3) moderate to high suicide risk based on PHQ-9 item 9 score, (4) current substance use disorder, and (5) current or past bipolar disorder.

There were 3 sequential steps in determining eligibility for participation in the study: an online screening survey, an intake phone call, and a clinical assessment.

Initial screening assessed inclusion criteria 1‐5. Individuals who satisfied screening criteria were emailed a link to read and sign a participant information and consent form.

Consenting men were telephoned by a psychologist for an intake call. The study was explained, and further screening and risk assessment were conducted. Men were screened for inclusion criterion 6 and exclusion criteria 1‐3. This call included a clinical risk assessment following a structured risk protocol. Those deemed to be at moderate to high risk for suicide were excluded and referred to receive immediate crisis attention (n=2). A clinical assessment was scheduled with those who satisfied eligibility criteria assessed as part of this intake call.

Following the intake call, eligible consenting fathers were assessed by a psychologist using the Quick Structured Clinical Interview for DSM-5 (QuickSCID-5 [38]) by telephone. Inclusion criterion 7 was assessed using the QuickSCID-5 assessment, as well as exclusion criteria 4 and 5. Results of the QuickSCID-5 were discussed with each prospective participant, and all were asked to nominate a general practitioner (previous, current, or newly identified) to whom the psychologist could send notification of their diagnosis, study participation, and treatment allocation.

DadBooster is a self-guided, web-based CBT program that was designed to be closely comparable in content to face-to-face treatment for depression and completed by participants at home. The program was supported by automated, one-way text messages sent twice weekly (11 messages in total over 6 weeks) to encourage engagement and introduce upcoming session content. The program was designed to treat depressive symptoms, with additional components included to support related domains such as parenting and couple relationship functioning.

DadBooster used tunnel information architecture to guide users through 6 sequential weekly sessions: (S1) getting started, (S2) managing your mood, (S3) increasing your pleasant activities, (S4) managing negative thoughts, (S5) increasing positive thoughts, and (S6) planning for the future. Sessions incorporated core CBT components, including psychoeducation about depression, mood monitoring, relaxation strategies, behavioral activation, cognitive restructuring, strategies to increase positive thinking, and relapse prevention. A scaffold approach was used to build upon content shown in previous sessions.

Each session was designed to be completed in approximately 20‐30 minutes and included text, audios, videos, and interactive activities to address the user’s individual issues and promote engagement. Between-session practice activities (“homework”) were recommended in every session. Feedback and reinforcement were provided within the program to support engagement and completion of homework activities. This was delivered via prerecorded session introduction videos presented by the program host, with content tailored based on the user’s activity completion.

The program included interactive charts that displayed user-entered data and depicted therapeutic concepts in CBT, such as the functional relationship between mood and pleasant activities. The user could personalize the program by changing the images that appear on each page to their own personal photos. Additional informational articles written specifically for the program were included in the DadBooster library, which users could access at any time. Topics covered were problem-solving strategies, stress management, time management, communication skills, information on enhancing relationships with partner and baby, getting support, and tips for caring for a baby. These articles were designed to directly target secondary outcome domains, particularly parenting and couple relationship quality, and to provide fathers with additional coping strategies.

Participants were encouraged to invite their partner to access a standalone partner support website, developed specifically for partners, with a separate user login. The partner support website included information for partners about caring for themselves and their baby and resources if they were struggling with postnatal depression themselves, while also providing information about paternal depression and what their partner may be experiencing.

The program included a printable workbook summarizing the activities completed in the program, and participants were encouraged to print it after session 6 as a hard copy reference. DadBooster was optimized for use on both desktop and mobile devices, and participants retained access for at least 6 months from enrollment. Minor refinements to the program were made during the trial to address technical issues and usability concerns identified by participants, without altering the core therapeutic content.

Adherence was measured unobtrusively using website analytics and database flags (see Intervention and Comparator Delivery section). A screenshot from session 4 is presented in Figure 1. The program is available from the Parent-Infant Research Institute [39].

As in the DadBooster condition, a letter was sent to the participant’s general practitioner (GP). General practitioners were notified that their patient met diagnostic criteria for depression, and they were encouraged to consult with their patient regarding their mental health care needs. Support and/or referral to other services then occurred as necessary, as would normally happen where specialized programs are not available. Therefore, routine care varied at the discretion of each general practitioner and included a mix of interventions or supports. Following completion of the 3-month postenrollment follow-up, participants in this group were provided with full access to DadBooster.

At baseline and at 12 weeks after enrollment, severity of depressive symptoms was measured online using the Depression Anxiety Stress Scales-21 (DASS-21 [40]). The DASS-21 is a 21-item, 4-point Likert-type scale. Each of the subscales (depression, anxiety, and stress) has a maximum score of 42. The Depression Anxiety Stress Scale (DASS) manual provides recommended cutoffs for rating the severity of depression as normal (0‐9), mild (10-13), moderate (14-20), severe (21-27), or extremely severe (28+).

At baseline and at 12 weeks after enrollment, psychologists trained to administer the QuickSCID-5 [38] conducted assessments by telephone to determine a Diagnostic and Statistical Manual of Mental Disorders-5 (DSM-5) diagnosis of current major depressive disorder or depressive disorder with insufficient symptoms. These psychologists were blind to treatment allocation at the 12-week follow-up time point.

After controlling for baseline DASS Depression scores, mean depression symptoms on the DASS Depression subscale at 12 weeks were significantly lower for the DadBooster condition than for the waitlist control condition (adjusted mean difference −7.26, 95% CI −11.34 to −3.18; F_1,47=12.81; P<.001; η_p²=0.21), indicating a very large effect size.

In the DadBooster condition, average scores on the DASS Depression subscale reduced from the high end of the “moderate” severity range (14-20) at baseline (mean 20.0, SD 7.1) to the “normal” range (0‐9) at 12 weeks (mean 5.7, SD 5.0). This represented an average 72% reduction in DASS Depression scores in the DadBooster condition, compared to a 40% reduction in the waitlist control condition (reduced from the “severe” range to “mild”; see Table 3 for means and SDs).

A contingency table and Fisher exact test were used to assess changes in depression diagnosis (QuickSCID-5), as the assumption of minimum expected cell frequency for chi-square was violated. In the DadBooster condition, 2 of 23 (9%) participants assessed still met diagnostic criteria for a depressive disorder at 12 weeks compared with 7 of 24 (29%) participants assessed in the waitlist control condition. The intention-to-treat analysis found that the association between condition and diagnosis was not significant (DadBooster: 2/25; waitlist control: 7/25; Fisher exact test: P=.14).

There was a significant interaction effect, indicating that the change in PHQ-9 scores over the course of the study time points was significantly different between the groups (Wilks Λ=0.74; F_4,45=4.00; P=.007; η_p²=0.26), representing a very large effect size (Figure 3). The main effect for time was also significant (Wilks Λ =0.22; F_4,45=39.45; P<.001; η_p²=0.78), indicating that there was a significant reduction in PHQ-9 scores over the 5 different time points. There was also a main effect for group (F_1,48=4.62; P=.04; η_p²=0.09), indicating that the 2 groups differed significantly in PHQ-9 scores.

After controlling for baseline DASS Stress scores, mean stress symptoms on the DASS Stress subscale at 12 weeks in the DadBooster condition were significantly lower than that in the waitlist control condition (adjusted mean difference −6.55, 95% CI −11.01 to −2.09; F_1,47=8.73; P=.005; η_p²=0.16), indicating a large effect size. Severity scores were in the “moderate” range for both conditions at baseline and reduced to the “normal” range in the DadBooster condition compared to the “mild” range in the waitlist control condition.

As the ANCOVA assumption, homogeneity of regression slopes, was violated for the DASS Anxiety subscale, a 2-tailed t test of difference scores was conducted. The change in anxiety symptoms over the study was not significantly different between the conditions (mean difference −3.40, 95% CI −7.03 to 0.23; t₄₈=−1.88; P=.07). Scores in the DadBooster condition decreased, on average, by 5.9 (SD 6.2) points, while scores in the waitlist control condition decreased, on average, by 2.6 (SD 6.6) points.

After controlling for baseline negative thinking (Automatic Thoughts Questionnaire) scores, mean negative thinking scores at 12 weeks in the DadBooster condition were significantly lower than that of the waitlist control condition (adjusted mean difference −18.10, 95% CI −29.79 to −6.42; F_1,47=9.71; P=.003; η_p²=0.17), indicating a large effect size. After controlling for baseline behavioral activation (Behavioral Activation for Depression Scale) scores, mean behavioral activation scores at 12 weeks in the DadBooster condition were not significantly different than that of the waitlist control condition (adjusted mean difference −4.72, 95% CI −13.91 to 4.46; F_1,47=1.07; P=.31; η_p²=0.02).

After controlling for baseline parenting self-efficacy (Parenting Sense of Competence Scale) scores, mean parenting self-efficacy scores at 12 weeks in the DadBooster condition were significantly higher than that of the waitlist control condition (adjusted mean difference 4.06, 95% CI 1.16-6.95; F_1,47=7.93; P=.007; η_p²=0.14), indicating a large effect size. After controlling for baseline relationship satisfaction (DAS-7) scores, mean relationship satisfaction scores at 12 weeks in the DadBooster condition were not significantly different than those of the waitlist control condition (adjusted mean difference 1.92, 95% CI −0.41 to 4.25; F_1,47=2.74; P=.11; η_p²=0.06).

In total, 96% (21/22) of DadBooster participants rated the program overall as “somewhat helpful” to “very helpful.” Participants were most satisfied with the strategies for reducing negative thinking and increasing positive thinking (see Table 4 for a breakdown of satisfaction with program features). Average scores on the System Usability Scale indicated acceptable usability of the DadBooster program (mean 71, SD 16).

Participants were interested in additional topics for library articles, with “Feeling angry and irritable” being the most requested (13/22, 59%), followed by “Men’s attitudes to seeking help” (10/22, 45%) and “Alcohol and substance use” (4/22, 18%). No other topics were suggested by participants.

The results were consistent with findings from our previous trials of MumMoodBooster [28,31]—the treatment for postnatal depression in mothers that inspired DadBooster. Participants in the DadBooster condition showed a significantly larger reduction in depression symptoms at 12 weeks compared to the waitlist control condition, with average symptom levels in the DadBooster condition reducing to the “normal” range [40]. Importantly, these results stand in contrast to the only published RCT of a digital intervention (mindfulness app) for postnatal depression in fathers [29], which reported no between-group differences in depression, anxiety, or stress, possibly due to low adherence to the intervention and moderate attrition over the study.

Visual inspection of the symptom trajectories suggests an initial reduction in depression symptoms in both conditions during the first few weeks following enrollment. However, the DadBooster condition appeared to show a more pronounced decline in symptoms over the remainder of the study, with a pattern consistent with continued improvement compared to the waitlist control. The initial reductions observed in both conditions may reflect potential benefits of the intake and assessment procedure, which included telephone contact, assessment and diagnosis with a psychologist, and a referral letter sent to each participant’s general practitioner. A recent meta-analysis showed that contact with a health professional prior to commencing an online treatment for depression (such as a diagnostic interview) is associated with better treatment outcomes [48].

A notable strength of this study was the inclusion of fathers who met clinical diagnostic criteria for depression. Several reviews have noted the lack of studies with men experiencing clinically significant depression [20,22], which has limited research on the suitability of interventions for this population. The only published trial of a digital intervention targeting postnatal depression in fathers [29] recruited a screened sample rather than requiring a formal clinical diagnosis for inclusion. In the present study, while severity of depression symptoms was significantly reduced following DadBooster, the between-group difference in remission rates did not reach statistical significance. However, the observed proportion of fathers still meeting diagnostic criteria for depression in DadBooster compared to waitlist control suggests a potential difference, consistent with the results observed for symptom severity. The lack of statistical significance may reflect the modest sample size and the additional support accessed by the waitlist control condition during the study period. More than three-quarters of the participants in the waitlist control condition sought additional support, most commonly from a health professional. In contrast, less than half of the fathers in the DadBooster condition sought additional support. This higher level of use in the waitlist control condition may have reduced between-group differences and thus provided a more conservative test of the intervention’s effects.

Consistent with findings from MumMoodBooster trials [28,31], fathers in the DadBooster condition demonstrated significantly greater reductions in stress compared to fathers in the waitlist control. However, no significant differences were observed for anxiety. Although depression and anxiety are highly comorbid [49], mean baseline anxiety scores were relatively low in both groups, falling within the “mild” range [40], which likely limited the scope for detectable improvement. In contrast, baseline stress scores were within the “moderate” range [40] for both groups, consistent with systematic review findings that fathers experience heightened stress during the perinatal period, contributing to mental health difficulties, such as depression [50]. Further, previous research suggests that men who strongly adhere to traditional masculine norms may conceptualize and describe their depression as “stress” [21]. Thus, reductions in perceived stress may represent an important and meaningful treatment outcome for fathers experiencing depression. The salience of stress among participating fathers may also be reflected in the program engagement data, with the “Managing your stress” article being the most frequently viewed resource in the DadBooster library.

Significant between-group differences were observed for automatic thoughts but not for behavioral activation. One possible explanation is that the competing demands of work, infant care, and partner support leave fathers with little time for self-directed activities [51], making behavioral activation strategies more challenging to implement. We can also speculate that men’s attitudes and traditional societal masculine norms—for example, expectations to be the provider, remain strong, prioritize others’ needs before their own, and support their partner—may have been a barrier to engaging in pleasant activities, consistent with literature on the association between adherence to masculine norms and men’s well-being behaviors [21]. It is possible that guilt associated with taking time out may have reduced engagement with the behavioral activation component of DadBooster. Research on CBT for men has highlighted the importance of addressing both cognitions and behaviors associated with traditional masculine norms when treating depression [52]. The findings of the present study may provide some insight into components of treatment specific to men that have been called for in previous reviews [20,52].

Importantly, significant between-group differences were found for parenting self-efficacy. This finding is noteworthy because a parent’s confidence in their ability to parent their child is strongly linked to more positive parent-infant interactions and improved child developmental outcomes [53]. The negative effects of postnatal depression in fathers on child outcomes are well-documented [14]. By strengthening parenting self-efficacy, the program may have broader implications for child outcomes, although this remains to be explored in future studies.

Consistent with MumMoodBooster trials [28,31], no significant between-group differences were observed in fathers’ relationships with their partners. Baseline scores for both conditions were within the “distressed” range. Elevated levels of relationship distress in this sample are consistent with previous research identifying relationship difficulties as a key challenge during the transition to fatherhood that can impact paternal mood [51]. Although some improvement in the couple relationship was noted in the DadBooster condition, average scores increased to just above the distressed threshold at 12 weeks [43]. However, less than half of the participants invited their partners to access the partner support website, and only one-third of participants’ partners accessed it. This may reflect the level of relationship distress and could have limited any potential benefits to their partners’ mental health and the couple relationship. It may also indicate adherence to traditional gender norms [20], where fathers feel the need to be strong and not burden their partners at a time when they may also be struggling. A proportion of partners may also have been experiencing their own mental health difficulties, given the established association between paternal and maternal depression in the postnatal period [13]. Future research could explore strategies to increase engagement with the partner support website, which also has links to support for postnatal depression in mothers, and could consider incorporating additional relationship-focused resources into the program.

Fathers in the DadBooster condition demonstrated high levels of engagement with the program, with most visiting 4 or more of the 6 sessions and, on average, visiting the program on several days. This level of program use is encouraging, as dropout rates tend to be higher in self-guided interventions than in guided interventions [54], and men are more likely to drop out [55]. The recent trial by Teague et al [29] reported low adherence among fathers to their mindfulness app and moderate attrition. It is possible that, in the present study, the intake and assessment calls with a psychologist may have been helpful for enhancing engagement with the DadBooster intervention, consistent with meta-analytic results showing that contact (eg, a diagnostic interview) prior to commencing online treatment is associated with greater adherence with the intervention [48]. Satisfaction with the program was also favorable, with almost all fathers indicating that they found the program to be “somewhat” to “very” helpful.