Approximately 90% of the body's serotonin is produced in the gut, which is part of the biological rationale for the gut-brain connection and the potential role of probiotics in mental health.
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Probiotics rank higher than many would expect, powered by a plausible mechanism: the vagus nerve connects gut and brain, GABA function in the brain is influenced by gut bacteria, and 90% of the body's serotonin is produced in the gut. Multiple studies find effect sizes of 0.5–0.7 for clinically diagnosed anxiety disorders, though the benefit is minimal for mild or subclinical anxiety. The major caveat is what one meta-analysis memorably called 'catastrophic heterogeneity' — the results and methodologies vary so wildly across studies that no coherent picture emerges on which strains work for which people. Drew predicts this area will become more powerful as personalized medicine develops the tools to match specific probiotic strains to specific individuals.
Multiple studies found effect sizes of 0.5 to 0.7 for probiotics in people with diagnosed anxiety disorders, though the benefit is minimal for mild or subclinical anxiety.
The widely cited ego-depletion model — the idea that willpower is a finite resource that gets depleted — failed to replicate in follow-up studies.
Humans are estimated to have 5,000–7,000 thoughts per day, yet can recall essentially none of them afterward, highlighting why in-the-moment emotional tracking matters.
A large Harvard study found that a wandering mind is an unhappy mind — people report greater happiness when their attention is tethered to the present, even if the task is unpleasant.
A key study finding that we have a 'credit card's worth of plastic' in our bodies was likely skewed because researchers used nitrile gloves that shed plastic particles onto the microplastic detector.
Emotionally sensitive people have a hyperactive amygdala, an underactive prefrontal cortex, and a frayed connection between the two — making emotional regulation structurally harder.
Rejection sensitivity can be observed as early as age 2 or 3, suggesting it has strong developmental and likely genetic roots.
A Yale study found that non-judgmental observation of emotions — without rushing to resolve them — reduces activation in the brain, making it a powerful regulation tool.
Dan Gilbert's research found that the psychological immune system — the brain's ability to justify and find satisfaction in choices — activates most powerfully when a decision is perceived as irreversible.
Barry Schwartz's research found that maximizers — people who try to optimize every decision — tend to achieve objectively better outcomes but report lower happiness than satisficers who choose 'good enough.'
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