[Solved] How does LSD work?

The effect of LSD on the brain is unique, profound, and very well researched. LSD acts on specific brain receptors and networks, causing perception, emotions, and consciousness to temporarily and fundamentally change. These neurobiological changes explain the rich visual and emotional experience, as well as the therapeutic potential.

What does LSD take effect on?

The most important place where LSD works is the 5-HT2A receptor. This is a serotonin receptor that is abundant in the cortex. LSD is a very potent partial agonist of this receptor. If you block this receptor with an antagonist such as ketanserine, both the subjective trip experience and the measurable changes in brain activity disappear.

Additionally, LSD binds to a lesser extent to receptors such as 5-HT1A, 5-HT2C, dopamine D2, α2-adrenergic receptors, and the recently identified TAAR1. These contribute primarily to the later phases of the trip, with mild sympathetic activation or motor restlessness.

What happens in the brain during an LSD trip?

Functionally, LSD lowers the internal network coherence of the Default Mode Network (DMN), particularly in the posterior cingulate cortex and medial prefrontal cortex. At the same time, the connectivity between networks to. This leads to a looser hierarchical structure in the brain and a state of increased network entropy — with more brain states and thus more flexibility in thinking and feeling.

In the sensory and visual cortex, hyperconnectivity actually arises. The primary visual cortex (V1–V4) shows increased blood flow and communication, which correlates strongly with visual hallucinations. The thalamus—which normally filters sensory input—shows looser 'gating' under LSD, allowing raw sensory information to reach the cortex more easily.

In the limbic system, particularly the amygdala and hippocampus, reactivity to fear stimuli decreases. This contributes to emotional processing and increased empathy, an effect that is also important in therapeutic contexts.

Which receptors control this process?

1. 5-HT2A on pyramidal cells → increased glutamate release, dysregulation of top-down control, increased sensory input.
2. 5-HT1A → inhibits serotonergic tone, supports introspective phases.
3. D2 → contributes to delayed agitation or possible delusions at high doses.
4. CAKE1 → influences dopamine and adrenaline release, role only recently recognized.

In summary: LSD works primarily through 5-HT2A receptors in brain regions such as the DMN, prefrontal cortex, visual cortex, and thalamus. It leads to DMN disintegration, increased network connectivity, more sensory input and high entropy in brain activity. These changes explain the onset of ego dissolution, hallucinations, and creative insights — the typical characteristics of an LSD experience.

More detailed explanation about this topic can be found on the page about the effects of LSD.