Accutane (Isotretinoin) Cognitive Function Impact: What the Evidence Actually Shows

Is there any human evidence that isotretinoin affects thinking or memory?

The drug labels do not report objective memory, attention or processing-speed tests before and after a course, and the cognitive experiments described below were done in mice. What exists for humans in the labeling is safety information.

The Absorica label lists depression, psychosis, suicidal thoughts and behavior, and aggressive or violent behaviors under psychiatric disorders, and directs prescribers to ask about psychiatric history before treatment and to assess for these symptoms at each visit [2]. The Accutane label's description of depression signs includes 'difficulty concentrating', alongside sad mood, hopelessness, fatigue and change in sleep pattern [3]. The neurological reaction lists in both labels include drowsiness, lethargy, dizziness, malaise and nervousness [2][3].

Those lists come from clinical trials and postmarketing reports, and the Accutane label notes that the relationship of some listed events to the drug is unknown [3]. 'Brain fog' is not a term either label uses, and neither label lists memory loss among its psychiatric or neurological reactions [2][3].

One cognition-related finding in the labeling concerns a different group: cases of IQ scores below 85 have been reported in children exposed to isotretinoin in the womb [2]. That statement is about prenatal exposure, not about the mental function of the person taking the capsules.

What did the animal studies actually show?

The experiment most often cited for a cognitive effect is a 2004 study by Crandall and colleagues in the Proceedings of the National Academy of Sciences. Mice given 13-cis-retinoic acid at 1 mg/kg/day, which the paper describes as a clinical dose, showed significantly reduced cell proliferation in the hippocampus and the subventricular zone, suppressed hippocampal neurogenesis, and severely disrupted learning of a spatial radial maze task [1]. These are the regions of the adult mouse brain where new neurons continue to be generated [1].

A second study, published in Neuropsychopharmacology in 2006, gave mice 1 mg/kg of 13-cis-retinoic acid daily by intraperitoneal injection for six weeks, a schedule that produced blood levels comparable to those reported in patients taking Accutane. Treated mice spent significantly more time immobile in the forced swim and tail suspension tests. There was no change in anxiety-related behavior in the open field test, and no impairment of locomotion in the open field or rotarod tests [4]. The authors read the immobility as depression-related behavior; it is not a measure of learning or memory.

Both are mouse experiments, each reported once. Neither measures anything in a person.

Why the brain is part of the conversation at all

A 2005 review by Lane and Bailey in Progress in Neurobiology describes what retinoid signaling does in the mature brain. Components of the retinoid metabolic pathway have been identified in adult brain tissue, suggesting that all-trans-retinoic acid can be synthesized in discrete brain regions; the distribution of retinoid receptor proteins in the adult differs from the pattern seen during development, with a likely physiological role in adult cortex, amygdala, hypothalamus, hippocampus, striatum and connected regions; and several neuron-specific genes contain recognition sequences for retinoid receptors and can be directly regulated by retinoids [5]. In rodent models, disrupting those pathways has been linked to changes in synaptic plasticity and to learning and memory behaviors, and retinoid signaling has also been implicated in Alzheimer's disease, schizophrenia and depression [5].

Isotretinoin is a retinoid that inhibits sebaceous gland function and keratinization, and its exact mechanism of action in acne is unknown [2]. The review above describes the brain's own retinoid system; it does not measure what a 15- to 20-week course of isotretinoin does to memory in a patient.

What the labels say, and what they tell prescribers to do

The Absorica label directs prescribers to ask patients and family members about any history of psychiatric disorder before starting treatment, and at each visit during treatment to assess for symptoms of depression, mood disturbance, psychosis or aggression. It also says that stopping treatment may be insufficient and that further evaluation may be necessary [2]. The Accutane label adds that while such monitoring may be helpful, it may not detect all patients at risk [3].

On reversibility, both labels state that of the patients reporting depression, some reported that the depression subsided with discontinuation of treatment and recurred with reinstitution of treatment [2][3].

Two structural points are easy to get wrong. Psychiatric disorders are handled in the Warnings and Precautions section of the label, not in the boxed warning; the boxed warning is embryo-fetal toxicity [2]. And the iPLEDGE REMS exists to mitigate that embryo-fetal risk [6].