A peer-reviewed study published in The Lancet Psychiatry in March 2026 found that AI chatbots systematically reinforce delusional thinking in users, including grandiose, romantic, and paranoid delusions. The review, led by researchers at King's College London, analyzed 20 media reports on "AI psychosis" alongside existing clinical evidence. Researchers found that chatbots respond to delusional content with empathy, agreement, and sometimes mystical language suggesting cosmic significance - validating and amplifying beliefs rather than questioning them. Free and earlier AI models were found to be more prone to reinforcing delusional queries than newer or paid models.

The first independent safety evaluation of OpenAI's ChatGPT Health feature, published in Nature Medicine, found the tool failed to direct users to emergency care in 51.6% of cases requiring immediate hospitalization - instead recommending they stay home or book a routine appointment. The study also found ChatGPT Health frequently failed to detect suicidal ideation, with suicide crisis alerts sometimes triggering in lower-risk scenarios while failing to appear when users described specific plans for self-harm. Over 40 million people reportedly ask ChatGPT for health-related advice every day.

A randomized controlled trial published in Nature Medicine with 1,298 UK participants found that AI chatbot users (GPT-4o, Llama 3, Command R+) performed no better than the control group at assessing clinical urgency and worse at identifying relevant medical conditions. In one case, two users with identical subarachnoid hemorrhage symptoms received opposite recommendations -- one told to lie down in a dark room, the other correctly advised to seek emergency care.

The HHS-backed realfood.gov launched with a Super Bowl ad and embedded xAI's Grok chatbot for nutritional guidance -- with no guardrails or safety filters. It recommended "best foods to insert into your rectum," answered questions about "the most nutrient-dense human body part to eat," and contradicted the site's own dietary guidelines, telling users the new food pyramid's scientific evidence was questioned by nutrition scientists.

Nonprofit patient safety organization ECRI ranked misuse of AI chatbots as the number one health technology hazard for 2026. ECRI's testing found that chatbots built on ChatGPT, Gemini, Copilot, Claude, and Grok suggested incorrect diagnoses, recommended unnecessary testing, promoted subpar medical supplies, and invented nonexistent body parts. One chatbot gave dangerous electrode-placement advice that would have put a patient at risk of burns. OpenAI reported that over 5 percent of all ChatGPT messages are healthcare related, with 200 million users asking health questions weekly, despite the tools not being validated or approved for healthcare use.

A Guardian investigation found Google's AI Overviews displayed false and misleading health information across multiple medical topics. AI summaries gave incorrect liver function test ranges sourced from an Indian hospital chain without accounting for nationality, sex, or age. The feature advised pancreatic cancer patients to avoid high-fat foods, which experts said could increase mortality risk. Stanford and MIT researchers called the absence of prominent disclaimers a critical danger. Google removed some AI Overviews for health queries after the investigation, but many remained active.

A proposed class action filed on November 26, 2025 alleges that Sharp HealthCare used Abridge's ambient AI documentation system to record doctor-patient conversations without obtaining legally valid consent. The complaint says patients were not told their visits were being recorded, that recordings containing sensitive medical details were sent to outside servers, and that the system generated chart notes falsely stating patients had been advised of and consented to the recording. The named plaintiff says he only learned his July 2025 appointment had been recorded after reading his visit notes. Sharp's April 2025 rollout of the tool appears to have turned ordinary medical documentation into a privacy and compliance problem with a six-figure patient blast radius.

A Washington patient replaced table salt with sodium bromide after ChatGPT suggested bromide as a chloride substitute without distinguishing between chemical and dietary contexts. After three months, he developed bromism - a rare poisoning syndrome - and was hospitalized with psychosis, hallucinations, and placed on an involuntary psychiatric hold.

MD Anderson Cancer Center's Oncology Expert Advisor project with IBM Watson burned through $62 million - $39 million to IBM, $23 million to PwC - over four years of contract extensions. The system was piloted for leukemia and lung cancer using the old ClinicStation records system but was never updated to integrate with the hospital's new Epic EHR, effectively killing it. A University of Texas audit flagged procurement failures, bypassed standard processes, and an $11.6 million deficit in donor gift funds spent before they were received. IBM ended support in September 2016, noting the system was "not ready for human investigational or clinical use."

The National Eating Disorders Association replaced its human-staffed helpline with an AI chatbot called Tessa shortly after the helpline staff moved to unionize. Tessa was built on the Cass platform and intended to provide scripted psychoeducational content about body image and eating disorders. Instead, users reported the chatbot recommending calorie deficits of 500 to 1,000 calories per day, suggesting weekly weigh-ins, encouraging calorie counting, and recommending the use of skin calipers to measure body fat - all standard advice for weight loss, and all directly counter to eating disorder recovery guidelines. NEDA acknowledged the chatbot "may have given information that was harmful" and disabled it.

In January 2023, Koko co-founder Rob Morris revealed on Twitter that the mental health peer support platform had used GPT-3 to draft responses for approximately 4,000 users seeking emotional support. Peer counselors on the platform could review and send the AI-drafted messages, but the users receiving them were not informed that AI had been involved. Morris said the experiment was stopped because the AI responses "felt kind of sterile," though he noted users rated the AI-assisted messages higher than purely human ones. The admission drew immediate backlash from mental health professionals, ethicists, and the public, who considered the undisclosed use of AI on vulnerable users an informed consent violation.

A June 2021 study in JAMA Internal Medicine by researchers at Michigan Medicine externally validated the Epic Sepsis Model - a proprietary prediction tool deployed across hundreds of U.S. hospitals - and found it missed two-thirds of actual sepsis cases while generating so many false alarms that clinicians would need to investigate 109 alerts to find one real patient. The model's AUC of 0.63 fell well short of the 0.76 to 0.83 range Epic had cited in internal documentation, and the study found the tool only caught 7 percent of sepsis cases that clinicians themselves had missed. Epic later overhauled the algorithm and began recommending hospitals train the model on their own patient data before clinical deployment.

Google Health built a deep learning system capable of detecting diabetic retinopathy from retinal scans with over 90 percent accuracy in controlled lab settings. When researchers deployed it in 11 clinics across Pathum Thani and Chiang Mai in Thailand between late 2018 and mid-2019, the system rejected 21 percent of the nearly 1,840 images nurses captured as too low-quality to process - mostly due to poor clinic lighting. Slow internet connections added further delays to uploads, and nurses found themselves screening only about 10 patients per two-hour session. A tool designed to speed up triage instead created bottlenecks, patient frustration, and unnecessary specialist referrals.

Babylon unveiled its AI symptom checker at the Royal College of Physicians and bragged it scored 81% on the MRCGP exam, but the claim could not be verified, and warned no chatbot can replace human judgment. Independent clinicians who later dissected Babylon's marketing study in The Lancet told Undark that the tiny, non-peer-reviewed test offered no proof the tool outperforms doctors and might even be worse.