Contents
Meta-analyses consistently indicate that mental health chatbots alleviate symptoms of both anxiety and depression. Although an effect size hovering around 0.3 remains modest within this academic field, it is nonetheless tangible. The core issue surfaces upon reviewing individual clinical trials one by one. Specifically, when a specialized therapy application was pitted against standard ChatGPT, the dedicated app failed to surpass the generic bot across any evaluated metric. Meanwhile, a six-week study tracking 540 participants revealed that the artificial intelligence variant boosted interaction frequency by 2.4 times and engagement duration by 3.8 times, yielding symptom reduction comparable to traditional static workbooks. Furthermore, a meta-analysis featuring a three-month post-intervention check demonstrated that the initial benefits had completely faded away. Five key metrics are thoroughly examined throughout this article.
The 30-second summary: the seven figures that matter
Each row names the study and the year. Always look at what the chatbot is being compared against.
| Finding | Result | Study and year |
|---|---|---|
| Effect on depression across 38 randomised trials | g = 0.31 (95% CI: 0.17-0.46), with 7,401 participants | Sohn et al., NPJ Digital Medicine (2026) |
| Effect on anxiety across 34 of those trials | g = 0.28 (95% CI: 0.05-0.51) | Sohn et al., NPJ Digital Medicine (2026) |
| Effect at three-month follow-up | No substantial effects on depression or anxiety | Zhong et al., J. Affect. Disord. (2024) |
| Therapy app against generic ChatGPT | No differences on any measure | Kuta et al., JMIR Mental Health (2025) |
| Use of an AI app against workbooks | 2.4 times the frequency and 3.8 times the duration | McFadyen et al., Comm. Medicine (2026) |
| Symptoms in that same comparison | Comparable: no added improvement in anxiety or depression | McFadyen et al., Comm. Medicine (2026) |
| Comparator in the most-cited trial | A waiting list with no access to any app | Heinz et al., NEJM AI (2025) |
What you will find here
• How much these systems reduce symptoms, according to the synthesis of 39 trials.
- The trial where the therapy chatbot drew level with plain ChatGPT.
• Why multiplying usage fourfold did not improve symptoms.
- What happened when measured three months after the conclusion.
The magnitude of the impact
The most recent and comprehensive synthesis was published by Jun-Seok Sohn and colleagues in NPJ Digital Medicine in 2026, searching five databases from 2017 with prior PROSPERO registration. Of 39 eligible randomised trials, 38 were analysed for depression, with 7,401 participants, and 34 for anxiety, with 7,621.
The pooled results: show a statistically significant decrease in depressive symptoms, yielding g = 0.31 (95% CI: 0.17-0.46), alongside a drop in anxiety symptoms, producing g = 0.28 (95% CI: 0.05-0.51). Standard measurement scales indicate these impacts remain modest.
There exists a helpful nuance within the subgroup analysis: the impact on depression proved greater among clinical and subclinical cohorts relative to non-clinical groups (p = 0.001). In other words, these interventions perform more effectively for individuals experiencing greater distress, which represents the preferred trajectory.
What that figure does not distinguish
An effect of 0.3 against a group receiving nothing is not the same as an effect of 0.3 against a reasonable alternative. Many of these trials compare the chatbot with a waiting list, that is, with doing nothing, and in mental health that systematically inflates the result through expectation, attention and the simple passage of time.
| Study | What it compared against | What it found | What it cannot support |
|---|---|---|---|
| Heinz et al., NEJM AI (2025) | Waiting list, with 210 adults over 4 weeks | The reference trial of an expert-fine-tuned chatbot | Without an active comparator, it cannot isolate the effect of receiving something |
| Kuta et al., JMIR Mental Health (2025) | Generic ChatGPT and a no-intervention group, 185 adults | Both reduce depression; between them, no difference | Small sample and a three-week intervention |
| McFadyen et al., Comm. Medicine (2026) | Digital cognitive behavioural therapy workbooks, 540 adults | Far more use, the same symptoms | Self-guided and unblinded |
| Sohn et al., NPJ Digital Medicine (2026) | Synthesis of 39 trials with any control | g = 0.31 on depression and 0.28 on anxiety | It pools very different comparators |
| Zhong et al., J. Affect. Disord. (2024) | 18 trials with 3,477 participants | Improvements at eight weeks and nothing at three months | Heterogeneous designs and therapeutic approaches |
The trial that compared against plain ChatGPT
This is the study that should circulate most and circulates least. Barbora Kuta and colleagues published in JMIR Mental Health in 2025 a trial with 185 adults split into three groups: a generative therapy app based on solution-focused therapy, general-purpose ChatGPT, and a no-intervention control group. Three weeks, nine planned sessions in each active group.
Compared to the control cohort, both active arms showed reductions in depressive symptoms according to the PHQ-9 inventory: d = −0.47 (p = 0.01) within the AI therapy cohort alongside d = −0.44 (p = 0.02) inside the ChatGPT cohort. Regarding anxiety levels and overall wellbeing, neither arm achieved statistical significance.
And the decisive result: the therapy app group did not outperform the ChatGPT group on any measure. Differences between the two were minimal and non-significant on depression, anxiety and wellbeing.
A small three-week trial should not be over-interpreted. But it does raise an uncomfortable question for the whole sector: if a tool designed specifically to do therapy cannot be told apart from a general-purpose chatbot, what is working may not be the therapeutic design.
Far more use, the same symptoms
The trial led by Jessica McFadyen and her team, featured in Communications Medicine in 2026, stands as the most extensive among the separate investigations: 540 adults across the United States dealing with heightened levels of anxiety or depression, whose study design was preregistered, were divided evenly between a cognitive behavioural therapy application driven by generative AI and digital workbooks based on the identical therapy, undertaken independently across a six-week duration.
| What was measured | AI app | Digital workbooks |
|---|---|---|
| Usage frequency | 2.4 times higher | Baseline |
| Usage duration | 3.8 times higher | Baseline |
| Anxiety symptoms (GAD-7) | Comparable | Comparable |
| Depression symptoms (PHQ-9) | Comparable | Comparable |
| Adverse events | No differences | No differences |
The authors’ conclusion is honest and applies across the field: in self-directed use, tailored generative-AI-enabled therapy safely enhances user engagement above and beyond static materials, without showing an overall enhancement in anxiety or depression symptom reduction.
Put another way: AI solves the problem of people abandoning these tools, which is real and important, and not the problem of making them work better. An exploratory analysis in the same work suggests that those who used the clinical personalisation features did see greater anxiety reduction, but that is a comparison between people who chose to use them, not a random assignment.
What is left three months later
Wei Zhong, Jiang-Hua Luo and Hong Zhang published a meta-analysis in the Journal of Affective Disorders in 2024 covering 18 randomised trials with 3,477 participants, searching five databases.
Their immediate results are consistent with the rest: improvements in depression (g = −0.26; 95% CI: −0.34 to −0.17) and anxiety (g = −0.19; 95% CI: −0.29 to −0.09), with maximum benefit after eight weeks of treatment.
And the figure that almost never makes the headlines: at three-month follow-up, no substantial effects were detected for either condition. The benefit exists while use continues and does not appear to leave anything behind.
That constraint links directly to a nuance within the domain’s foundational study, conducted by Michael Heinz and co-authors and published in NEJM AI in 2025, which evaluated an expert-adapted generative chatbot involving 210 adults with clinically significant symptoms of major depression, generalised anxiety or high risk for an eating disorder. The control cohort relied on a waiting list with no access to any app throughout the four-week investigation. Such a setup invariably maximizes apparent outcomes, and this very methodology drives a significant share of the broader public discourse surrounding the topic.
What to do with this, in practice
Ordered by the strength of the evidence behind it:
• Ask what it was compared against before believing a figure. A waiting list is not an active comparator, and many of these trials use one.
• Do not expect the effect to last. The meta-analysis with three-month follow-up found no substantial effects on depression or anxiety.
• If the goal is retention, AI does deliver. It multiplied usage frequency by 2.4 and duration by 3.8 against static materials.
• Do not assume a specialised tool is better. In the only trial that compared them, it did not outperform generic ChatGPT on any measure.
• Treat it as a supplement in mild or moderate cases. The pooled effect, g = 0.31, is real but small, and larger in clinical samples than in the general population.
Frequently asked questions
Do therapy chatbots work?
They have a real, small effect. The meta-analysis of 39 randomised trials published in NPJ Digital Medicine in 2026 estimates a reduction in depressive symptoms of g = 0.31 (95% CI: 0.17-0.46) with 7,401 participants, and in anxiety symptoms of g = 0.28 (95% CI: 0.05-0.51), with larger effects in clinical and subclinical samples than in the general population.
Does the improvement hold over time?
The available evidence says no. The meta-analysis of 18 trials with 3,477 participants found improvements in depression (g = −0.26) and anxiety (g = −0.19), peaking at eight weeks, but detected no substantial effects at three-month follow-up.
Does a therapy app surpass using ChatGPT directly?
In the solitary trial that evaluated them, negative. Among 185 adults divided between a generative therapy application, standard ChatGPT and a control cohort, both active arms decreased depression relative to the control (d = −0.47 alongside d = −0.44), while the dedicated app failed to surpass ChatGPT across any metric. It represents a modest, three-week investigation.
What is the actual purpose of AI within these applications?
Above all, when it comes to encouraging adoption. During the study involving 540 subjects, the generative-AI variant boosted usage frequency by a factor of 2.4 and session length by 3.8 relative to conventional digital workbooks addressing the same therapy, yielding similar outcomes for anxiety and depression alongside identical adverse event rates. High attrition plagues digital interventions, and this is precisely where the solution proves beneficial.
Why does the comparison group matter so much?
Because it changes the reading of the result entirely. The field’s most-cited trial, published in NEJM AI in 2025 with 210 adults with clinically significant symptoms, compared the chatbot with a waiting list that had no access to any app. Against receiving nothing, almost any intervention improves measured symptoms.
What we do not know
• How they compare with human therapy. None of these trials contrasts the chatbot with equivalent face-to-face psychotherapy.
• What happens in a crisis. Trials usually exclude people at acute risk, who are precisely the greatest concern.
- Whether the impact stems from the material or the interaction itself. The appeal seen with a standard chatbot implies that therapeutic structuring might not be the defining element.
• Almost nothing in adolescents and older adults. The 2026 review explicitly notes the absence of studies in those two age groups.
References
1. Sohn, J.-S., Ha, B.-G. et al. Systematic review and meta analysis of chatbots in the management of depressive and anxiety symptoms. NPJ Digital Medicine, 2026. DOI: 10.1038/s41746-026-02566-w
2. Kuta, B., Novak, L. et al. Effectiveness of a Fully Automated Mobile Therapeutic Versus a General Chatbot in Reducing Depression and Anxiety and Improving Well-Being. JMIR Mental Health, 2025. DOI: 10.2196/82642
3. McFadyen, J., Habicht, J. et al. Increasing engagement with cognitive-behavioral therapy (CBT) using generative AI: a randomized controlled trial. Communications Medicine, 2026. DOI: 10.1038/s43856-025-01321-8
4. Zhong, W., Luo, J.-H. and Zhang, H. The therapeutic effectiveness of artificial intelligence-based chatbots in alleviation of depressive and anxiety symptoms in short-course treatments. Journal of Affective Disorders, 2024. DOI: 10.1016/j.jad.2024.04.057
5. Heinz, M. V., Mackin, D. M. et al. Randomized Trial of a Generative AI Chatbot for Mental Health Treatment. NEJM AI, 2025. DOI: 10.1056/aioa2400802
This material is purely informational and does not serve as medical or psychological guidance, nor does it substitute for treatment provided by a mental health expert. Should you find yourself in a dangerous situation, please reach out to your nearest emergency services or crisis hotline.
