What is Kratom and How Does It Affect the Brain?
Kratom (Mitragyna speciosa) is a tropical tree native to Southeast Asia, where its leaves have been used for centuries in traditional medicine [1.7.2]. In the United States and other Western countries, it has gained popularity as an herbal supplement for pain relief, to mitigate opioid withdrawal symptoms, and for its mood-lifting effects [1.7.3]. The plant's effects are dose-dependent: at low doses, it acts as a stimulant, producing increased energy and alertness, while at high doses, it has sedative, opioid-like effects [1.7.2].
The primary psychoactive compounds in kratom are the alkaloids mitragynine and 7-hydroxymitragynine [1.2.1]. These compounds are considered atypical opioids because they act as partial agonists at the mu-opioid receptors in the brain, the same receptors activated by drugs like morphine [1.2.1, 1.7.3]. However, their action is distinct and also involves other neurotransmitter systems, including serotonin, dopamine, and adrenergic receptors [1.3.2, 1.8.1]. Because mitragynine can cross the blood-brain barrier, it can directly influence multiple neural systems that regulate brain functions, including cognition [1.8.1].
The Link Between Kratom Use and Memory Problems
Scientific evidence on kratom's cognitive effects points towards a significant connection between chronic, high-dose use and memory impairment. Animal studies consistently show that high doses of mitragynine can impair various aspects of memory, including spatial learning, reference memory, and object recognition [1.2.1, 1.3.3, 1.3.4]. Research suggests these deficits may be caused by the disruption of synaptic plasticity—the process by which connections between neurons are strengthened or weakened, which is crucial for learning and memory [1.8.4, 1.9.1]. Specifically, higher doses of mitragynine have been shown to inhibit long-term potentiation (LTP), a key cellular mechanism for memory formation, in the hippocampus [1.4.4, 1.8.1].
Human studies, while more limited, show similar trends. One study on regular users found that high consumption (>3 glasses of kratom tea daily) was selectively associated with deficits in visual episodic memory and new learning [1.3.2]. Other reports from long-term users mention poor attention, difficulty concentrating, and memory deficits [1.8.1, 1.3.1]. Some users also report experiencing cognitive instability and "brain fog" with regular use [1.3.1].
Short-Term vs. Long-Term Cognitive Effects
The impact of kratom on memory largely depends on the duration and frequency of use.
Short-Term Effects: In the short term, particularly at low doses, some users report stimulant-like effects such as increased focus and energy [1.7.2]. However, even acute administration of mitragynine has been shown in animal studies to disrupt memory formation, consolidation, and retrieval [1.2.1]. At higher doses, the sedative effects become more prominent, which can indirectly impair cognitive functions and memory encoding [1.7.2].
Long-Term Effects: Chronic, high-dose use poses a more significant risk. Long-term use can lead to dependence, addiction, and withdrawal [1.3.1]. Animal studies have demonstrated that chronic mitragynine exposure is associated with cognitive impairments [1.8.2]. Furthermore, use during adolescence may cause long-lasting cognitive deficits that persist into adulthood, highlighting the vulnerability of the developing brain [1.3.4, 1.2.5]. Some of the cognitive impairment caused by lower doses may be reversible after a period of abstinence [1.2.1].
Comparison Table: Kratom vs. Traditional Opioids on Cognition
| Feature | Kratom | Traditional Opioids (e.g., Morphine) |
|---|---|---|
| Primary Active Compounds | Mitragynine, 7-hydroxymitragynine [1.2.1] | Morphine, Codeine |
| Receptor Action | Partial agonist at mu-opioid receptors; also affects serotonin and adrenergic systems [1.3.2] | Full agonist at mu-opioid receptors |
| Cognitive Effects | Dose-dependent: stimulating at low doses, sedating and potentially memory-impairing at high doses [1.7.2] | Primarily sedating; well-documented to impair memory and cognitive function with chronic use [1.2.1]. |
| Memory Impairment Risk | Linked to long-term, high-dose use; may affect visual learning and executive function [1.3.1, 1.3.2]. | Established risk, particularly with chronic use and abuse, affecting various memory domains [1.2.1]. |
| Addiction Potential | Poses risks of addiction, abuse, and dependence [1.3.1]. The DEA lists it as a "Drug of Concern" [1.7.2]. | High risk of physical and psychological dependence and addiction. |
| Withdrawal & Cognition | Withdrawal can cause significant cognitive issues, including "brain fog," anxiety, and memory problems [1.5.2, 1.5.3]. | Withdrawal involves severe mood and cognitive disturbances [1.5.2]. |
Kratom Withdrawal and 'Brain Fog'
For individuals who develop a dependence on kratom, stopping or reducing use can trigger a withdrawal syndrome similar to that of opioids [1.5.2]. In addition to physical symptoms like muscle aches and nausea, the psychological and cognitive symptoms can be particularly challenging. Many people report experiencing intense "brain fog," which is characterized by mental confusion, difficulty concentrating, and short-term memory lapses [1.3.1, 1.5.3]. Animal studies have confirmed that withdrawal from mitragynine can induce cognitive deficits, which may be linked to changes in the hippocampus [1.4.2].
Conclusion: A Dose-Dependent Risk
The available evidence strongly suggests that kratom can cause memory problems, but this risk is not uniform and is heavily influenced by the dose, frequency, and duration of use. While low, occasional doses might not pose a significant threat to cognitive function and may even have stimulating effects, chronic and high-dose consumption is clearly associated with impairments in learning, memory, and executive function [1.3.1, 1.8.1]. These effects are rooted in kratom's opioid-like action and its ability to alter brain plasticity [1.4.4]. Furthermore, cognitive difficulties are a prominent feature of kratom withdrawal [1.5.3]. As kratom is unregulated in the U.S. by the FDA, its potency and purity can vary, adding another layer of risk [1.10.4]. Anyone considering using kratom should be aware of these potential cognitive consequences.
For more information, consult resources from the National Institute on Drug Abuse (NIDA).
