David Nutt

David Nutt’s role in the account runs along two tracks: he publicly challenged official judgments about drug risk, and he helped make a once far-fetched psychedelic research program possible. At Imperial College London, his collaboration with Robin Carhart-Harris and Amanda Feilding carried brain-imaging research toward a clinical question: whether psilocybin might relieve treatment-resistant depression.

Identity and public position

Nutt is an English psychopharmacologist with expertise in addiction and benzodiazepines, including Valium. He chaired the government’s Advisory Council on the Misuse of Drugs, the committee responsible for advising on the classification of illicit drugs according to their risks to individuals and society. His approach was to compare substances by empirical estimates of harm rather than accept the distinctions built into their legal status.

That method made his conclusions politically combustible. Nutt argued that alcohol was more dangerous than cannabis and that using Ecstasy was safer than riding a horse. In 2009, after he had become a prominent critic of government drug policy, the Home Secretary dismissed him from the council. The episode made his research and public role inseparable: evaluating risk was not only a technical task, but a challenge to the assumptions behind official classifications.

The confrontation sharpened during a live breakfast television appearance. Asked whether he was seriously claiming that LSD was less harmful than alcohol, Nutt answered that he was. The book presents this statement as the sentence that led to his dismissal. His case exemplified the tension between a scientific adviser’s effort to compare evidence consistently and a government’s authority to set policy, even when the two judgments diverge.

Building a research partnership

In 2005, Robin Carhart-Harris approached Nutt hoping to study psychedelics and dreaming. Carhart-Harris raised the possibility that Amanda Feilding’s foundation might fund the work. Nutt initially judged the proposed project too speculative for a young researcher without neuroscience experience. But Carhart-Harris persisted, and Nutt offered him a PhD, proposing that he begin with a more conventional study of MDMA’s effects on the serotonin system, with psychedelic research as a possible later direction.

That sequence matters: the psychedelic project did not begin as an already-established laboratory program. Carhart-Harris first completed the PhD and joined Nutt’s lab; Feilding supplied funding; and Nutt’s support helped turn the original ambition into a research plan. By 2009, the team had received approval from the National Health Service and the Home Office to study psilocybin’s effects on the brain. LSD research followed a few years later.

Carhart-Harris volunteered to be the first participant, reasoning that it would be honest to undergo the procedure before asking others to receive the drug in a scanner. Nutt dissuaded him: Carhart-Harris had described himself as anxious, and Nutt also worried that participation could compromise his objectivity. A colleague instead received psilocybin and entered the fMRI scanner. Nutt’s intervention thus helped define the boundary between the investigator’s personal commitment to a study and the safeguards required for research.

What the brain scans changed

The team had expected psilocybin to increase brain activity, especially in regions associated with emotion. Earlier work by Franz Vollenweider had also indicated stimulation, particularly in the frontal lobes. The first Imperial data appeared to show the opposite: decreased blood flow, concentrated in the default mode network. A second measure, based on oxygen consumption, supported the initial finding. The result redirected attention from a simple picture of psychedelic stimulation toward a network whose activity appeared to diminish while other regions became more active.

The default mode network is presented as exerting a regulatory influence over other brain systems. In the account’s explanatory model, its activity helps constrain both internally arising material and the sensory information admitted to consciousness. It acts like a filter, permitting only a limited portion of the information available to the brain. Nutt’s pointed question was why ordinary consciousness should be so constrained rather than more open. The answer may involve efficiency: the brain forms perceptions by using limited sensory evidence and prior experience to make predictions about the world.

When psychedelic drugs reduce default-mode activity, other regions, including those involved in emotion and memory, may be less inhibited. This offers a possible account of why feelings, memories, or childhood experiences that are not readily accessible in ordinary waking consciousness can come into awareness. It also makes the proposed therapeutic value intelligible: researchers could investigate whether a change in these constraints helps people encounter material connected with rigid or distressing mental patterns. The explanation remains a model of how the experience might work, not proof that every such experience has the same cause or effect.

From neuroscience to a clinical trial

After publishing his account of the brain’s entropy, Carhart-Harris sought to test the theories in patients. Nutt secured a grant from the U.K. government for a small pilot study of psilocybin for treatment-resistant depression: a condition defined here by patients’ failure to respond to usual therapies and medications. This marked a change in the lab’s work, from investigating psychedelic effects to studying a possible clinical application.

The transition also brought a practical and ethical difficulty into view. Carhart-Harris’s lab had little experience with clinical work, and research goals could conflict with a participant’s immediate welfare. In an LSD experiment that was not a clinical trial, a volunteer became anxious in the scanner and asked to leave. After a break, he agreed to return, but his anxiety recurred; he again asked to get out and tried to leave. The researchers persuaded him to remain and administered a sedative. The episode is not presented as an outcome of the depression pilot, but as an early warning about the responsibilities involved when an experiment requires both the collection of data and attention to a participant in distress.

Nutt’s contribution therefore extends beyond an endorsement of psychedelic research. His policy advocacy made drug-risk comparisons publicly contentious; his partnership with Carhart-Harris and Feilding supported a line of research that challenged expectations about brain activity; and his grant-getting brought that research toward a pilot treatment study. Together, these roles show how a change in scientific understanding depends not only on a striking result, but also on the institutional access, funding, and judgment needed to pursue it.