Classic Psychedelic Drugs: Update on Biological Mechanisms

Summary & key facts

Researchers reviewed animal and human studies from the last two decades to understand how classic psychedelic drugs work in the brain. They found that these drugs mainly act on certain serotonin receptors in brain circuits that link sensation, thinking, emotion, and the sense of self. Psychedelics change the balance between signals that turn brain cells on and off and can encourage the brain to rewire itself. Brain scans show that the special feelings people report on psychedelics go along with clear changes in activity and connections across multiple brain systems. These brain changes might help explain why psychedelics are being studied as treatments for mental health problems, but the review does not claim they are proven therapies yet.

Key facts:

• The authors looked at modern studies in animals and people to learn how classic psychedelics affect the brain.
• Psychedelics mainly work on specific serotonin receptors, which respond to the brain chemical serotonin.
• These drugs act in brain loops that connect the cortex to the thalamus and other cortex areas, which are important for processing information.
• Psychedelics change the balance between signals that excite neurons and signals that inhibit them. In other words, they alter how strongly parts of the brain turn on or off.
• They can promote neuroplasticity, which is the brain's ability to change its wiring and connections.
• Neuroimaging studies found that the kinds of experiences people describe on psychedelics and changes in self-related thinking and emotion regulation match distinct changes in brain activity and connectivity.
• The review suggests that changes in how people experience themselves, process emotions, and relate to others may be part of why psychedelics could help with some psychiatric conditions, but it stops short of saying this is proven.

Abstract

Renewed interest in the effects of psychedelics in the treatment of psychiatric disorders warrants a better understanding of the neurobiological mechanisms underlying the effects of these substances. During the past two decades, state-of-the-art studies of animals and humans have yielded new important insights into the molecular, cellular, and systems-level actions of psychedelic drugs. These efforts have revealed that psychedelics affect primarily serotonergic receptor subtypes located in cortico-thalamic and cortico-cortical feedback circuits of information processing. Psychedelic drugs modulate excitatory-inhibitory balance in these circuits and can participate in neuroplasticity within brain structures critical for the integration of information relevant to sensation, cognition, emotions, and the narrative of self. Neuroimaging studies showed that characteristic dimensions of the psychedelic experience obtained through subjective questionnaires as well as alterations in self-referential processing and emotion regulation obtained through neuropsychological tasks are associated with distinct changes in brain activity and connectivity patterns at multiple-system levels. These recent results suggest that changes in self-experience, emotional processing, and social cognition may contribute to the potential therapeutic effects of psychedelics.

Topics

Biochemical Analysis and Sensing Techniques Neurotransmitter Receptor Influence on Behavior Psychedelics and Drug Studies

Categories

Clinical Psychology Psychology Social Sciences

Tags

Affect (linguistics) Cognition Cognitive psychology Communication Internal medicine Medicine Neuroimaging Neuropsychology Neuroscience Psychology Receptor Serotonergic Serotonin

Substances

Ayahuasca LSD Psilocybin

Conditions & symptoms

Anxiety Depression PTSD Anxiety or worry Feeling disconnected from others Sadness or low mood