Summary: A new hypothesis suggests that psychedelics may enhance empathy, insight, and psychological flexibility by transiently shifting brain function toward the right hemisphere. Called HEALS—Hemispheric Annealing and Lateralization Under Psychedelics—this model proposes that psychedelic experiences temporarily reverse the usual left-dominant hierarchy between hemispheres, freeing the right hemisphere’s more holistic, emotionally attuned processing from left-brain constraints.
Neuroimaging studies reviewed in the proposal report a rightward shift in brain activity during psychedelic states. That lateral shift aligns with many qualities commonly reported after psychedelic use—heightened mindfulness, greater emotional sensitivity, increased creativity, expanded attention to novelty, and clearer personal insight. The HEALS model links those psychological effects to measurable changes in hemispheric activity.
Key facts:
- HEALS model: Psychedelics may shift functional dominance from the left to the right hemisphere.
- Emotional and cognitive benefits: Right-hemisphere predominance could underlie gains in empathy, creativity, insight, and psychological flexibility.
- Neural evidence: Imaging studies show increased right-hemisphere blood flow and metabolic activity under psychedelics.
Source: Ohio State University
Overview
Researcher Adam Levin, combining clinical experience in psychiatry and therapeutic psychedelics research with a broad review of imaging studies and prior theories, has outlined the HEALS hypothesis in the Journal of Psychopharmacology. Rather than simply cataloguing what each hemisphere does, Levin focuses on how the hemispheres typically approach information and tasks in concert—and how psychedelics appear to change that balance.
Under ordinary waking consciousness, the hemispheres operate in parallel but with a leftward dominance: the left hemisphere narrows attention to individual parts and manipulates details, while the right hemisphere maintains broader, contextual and integrative perspectives. Levin suggests psychedelics temporarily reverse this relationship, releasing the right hemisphere from left-hemisphere inhibition and creating a novel interaction between the two modes of processing.
Levin describes the psychedelic state as a distinctive reunion of left- and right-hemisphere perspectives that rarely occurs during normal waking life. He calls this hypothesized mechanism Hemispheric Annealing and Lateralization Under Psychedelics—HEALS. In his view, this atypical annealing toward right-hemisphere predominance helps explain commonly observed psychedelic outcomes: widened attention, enhanced social and emotional intelligence, flashes of creative insight, and experiential clarity that can prompt psychological and therapeutic change.
Levin drew inspiration from earlier thinkers such as Iain McGilchrist, author of The Master and His Emissary, and from his own clinical observations during medical training and psychiatric residency. He notes striking parallels between symptoms seen after damage to one hemisphere and the altered perspectives reported in psychedelic sessions. For example, right-hemisphere stroke patients often exhibit a narrowed attentional window and diminished awareness of half the visual field, while left-hemisphere loss can leave a broader, integrative view intact—patterns that echo contrasts between left- and right-dominant processing.
Previous models of psychedelic action emphasized a general relaxation of frontal and top-down control—“unrestrained cognition.” Levin acknowledges that explanation but argues the HEALS model adds a lateral dimension: many psychedelic effects—improved empathy, expanded sense of connection, increased creativity, and greater clarity about one’s life—map closely onto functions associated with the right hemisphere. In other words, psychedelics may not simply reduce top-down constraint; they may also scaffold a temporary right-hemisphere predominance that offers access to a different, more holistic style of perception and feeling.
Levin’s review of neuroimaging evidence highlights lateralized changes in blood flow and glucose metabolism consistent with enhanced activity in right frontal and related networks during psychedelic states. He further notes that regular mindfulness meditation, which is linked to increased right-hemisphere network strength and cortical thickness, produces effects similar to those reported after psychedelic use—sometimes after only one or two sessions. This overlap suggests psychedelics could briefly amplify right-sided networks that meditation strengthens over time, potentially creating opportunities to consolidate and sustain increased mindfulness and emotional awareness after the acute drug effects subside.
While the primary thrust of contemporary psychedelic research focuses on therapeutic applications—such as treating depression, PTSD, and addiction—Levin expects the expanding field will also test mechanistic theories like HEALS. He frames HEALS as complementary to existing explanations, arguing that multiple theoretical perspectives will be necessary to capture the brain’s complexity. Overreliance on any single account risks missing important aspects of psychedelic action, he warns.
About this psychopharmacology and neuroscience research news
Author: Emily Caldwell
Source: Ohio State University
Contact: Emily Caldwell – Ohio State University
Image: The image is credited to Neuroscience News
Original research: Open access. “Hemispheric annealing and lateralization under psychedelics (HEALS): A novel hypothesis of psychedelic action in the brain” by Adam Levin et al., Journal of Psychopharmacology.
Abstract
Hemispheric annealing and lateralization under psychedelics (HEALS): A novel hypothesis of psychedelic action in the brain
Existing models of psychedelic action have emphasized changes along dorsal–ventral and anterior–posterior brain axes but have largely overlooked lateral differences between hemispheres. The HEALS model proposes that psychedelics reverse the usual hierarchical arrangement between hemispheres: under typical consciousness the hemispheres act in parallel with left-hemisphere predominance, whereas under psychedelics and some other altered states of consciousness this hierarchy flips and the right hemisphere is released from left-hemisphere inhibition.
Levin reviews available neuroimaging evidence for lateralized effects under psychedelics and contrasts cognitive and emotional changes observed during psychedelic experiences with known hemispheric specializations. Functions considered include attention, social and emotional intelligence, creativity and insight, and language. The review also examines laterality in other altered states—such as meditation and trance—and suggests that many psychedelic phenomena may result from an atypical annealing between hemispheres toward right-hemisphere predominance.