Oral Cannabis Impaired Memory and Damaged Brain Structures in Rats | Research

The takeaway

Seven days of oral cannabis administration in rats impaired spatial memory and caused visible damage to neurons in the cerebral cortex and hippocampus.

Read this if you are interested in how cannabis edibles might affect brain structure and memory.

7 days of oral cannabis caused spatial memory impairment comparable to a known memory-disrupting drug

What the researchers found

Rats given oral cannabis extract (20 mg/kg) daily for seven consecutive days showed significant cognitive and neurological impairments compared to controls.

In the Open Field Test, cannabis-treated rats showed reduced rearing (exploratory behavior) and increased freezing, indicating decreased curiosity and increased anxiety-like behavior. In the Elevated Plus Maze, rearing was also reduced, further supporting anxiogenic effects.

Spatial memory was impaired as measured by the Y-maze, with cannabis-treated rats showing reduced percentage alternation similar to rats given scopolamine, a drug known to impair memory.

Histopathological examination revealed alterations in neuronal architecture in both the cerebral cortex and hippocampus, providing a structural basis for the observed cognitive deficits.

Why it matters

This study demonstrates that even relatively short-term oral cannabis exposure can produce measurable cognitive deficits and visible brain changes in a controlled animal model. The oral administration route is particularly relevant given the growing popularity of cannabis edibles.

The numbers in context

18 rats across 3 groups. Cannabis dose: 20 mg/kg daily for 7 days. Cannabis-treated rats showed reduced rearing frequencies and impaired Y-maze alternation comparable to scopolamine-treated animals.

How the study worked

Eighteen adult Wistar rats were randomly assigned to three groups: saline control, cannabis extract (20 mg/kg oral, 7 days), and scopolamine (1 mg/kg intraperitoneal, as a positive control for cognitive impairment). Behavioral assessments included the Open Field Test, Elevated Plus Maze, and Y-maze. Brains were subsequently examined histopathologically.

What this study cannot tell us

Very small sample size (6 per group). Only a single dose was tested for a single duration. The cannabis extract composition and THC concentration were not specified in the abstract. Rat brain development differs from human brain development. Short observation period prevents assessment of whether effects reverse after discontinuation.

How to read the evidence

Small animal study with limited sample size and single dose. Preliminary evidence requiring replication with larger samples and dose-response designs.

When this study was published

Published in 2017.

The bigger picture

While animal studies have limitations in predicting human outcomes, the combination of behavioral deficits (impaired spatial memory) with histological changes (damaged cortical and hippocampal neurons) strengthens the case that cannabis can affect brain structure and function, not just behavior.

Questions still open

Are the brain changes reversible after cannabis cessation? Would lower doses or shorter exposure produce the same effects? How does the 20 mg/kg dose in rats translate to typical human edible consumption?

Common questions

Can cannabis edibles damage the brain?

This rat study found that 7 days of oral cannabis caused visible changes to neurons in the cortex and hippocampus alongside memory impairment. However, translating animal findings to human edible use requires caution given differences in dosing, metabolism, and brain biology.

Does cannabis impair memory?

In this study, cannabis-treated rats showed impaired spatial memory in the Y-maze test, performing similarly to rats given a drug known to disrupt memory. This adds to broader evidence linking cannabis exposure to short-term cognitive deficits.

Read the original research

Repeated Acute Oral Exposure to Cannabis sativa Impaired Neurocognitive Behaviours and Cortico-hippocampal Architectonics in Wistar Rats.

Nigerian journal of physiological sciences : official publication of the Physiological Society of Nigeria, 31(2), 153-159

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Citation

Imam, A; Ajao, M S; Akinola, O B; Ajibola, M I; Ibrahim, A; Amin, A; Abdulmajeed, W I; Lawal, Z A; Ali-Oluwafuyi, A. (2017). Repeated Acute Oral Exposure to Cannabis sativa Impaired Neurocognitive Behaviours and Cortico-hippocampal Architectonics in Wistar Rats.. Nigerian journal of physiological sciences : official publication of the Physiological Society of Nigeria, 31(2), 153-159.