Dr. Kevin Mitchell is a neurogeneticist at Trinity College Dublin and author of Innate and Free Agents, two very influential books on how brain wiring shapes who we become.

Autism is one of the most heritable conditions in psychiatry — yet for years, headlines have claimed gut bacteria, probiotics, and mouse models could explain or even treat it. Kevin’s new paper tears that story open, revealing how tiny samples, noisy data, and weak statistics created an illusion of evidence that never truly existed.

Expect to learn why early microbiome studies were almost guaranteed to produce false positives, how mouse “models of autism” rely on behaviours that barely map onto human symptoms, why effect sizes of ~1.1 don’t mean what people think, what proper replication actually looks like, why placebo-controlled trials keep finding nothing, how hype and incentives distort entire fields, and how bad science creates real-world harm for autistic people and their families.

Timestamps:

03:30 Introduction and Gratitude

04:30 The Link Between Gut Microbiome and Autism

07:08 The Tylenol Controversy and Misinterpretation of Data

11:24 The Complexity of Autism and Its Causes

16:12 Exploring the Gut-Brain Axis

25:34 Evidence Line 1: Human Observational Data

42:42 Understanding Causation in Microbiome Research

45:16 The Role of Effect Size in Autism Studies

48:04 Confounding Factors in Scientific Research

54:30 Evidence Line 2: Mouse Models of Autism

59:20 The Limitations of Germ-Free Mouse Studies

01:05:45 Statistical Flaws in Microbiome Research

01:13:14 Skepticism in Behavioural Studies and Drug Testing

01:17:15 Understanding Autism's Heterogeneity

01:19:14 The Challenges of Diagnosing Autism

01:24:35 Evidence Line 3: Human Trials

01:29:28 The Importance of Placebo-Controlled Trials

01:34:42 The Role of Citations in Scientific Literature

01:40:15 The Ethics of Marketing Probiotics for Autism

01:45:17 Current Research and Future Directions

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#78 Dr Kevin Mitchell: Bad Science, Autism, Tylenol & The Gut Microbiome!