"I can't think straight, I'm too stressed" turns out to be a fairly literal description of what's happening in the brain, not just a figure of speech.
The Hippocampus Connection
The hippocampus — central to forming new memories — is particularly sensitive to cortisol, the primary human stress hormone. In controlled studies, administering high doses of cortisol to healthy subjects selectively impaired verbal declarative memory (the kind involved in recalling facts and conversations), without affecting other types of memory that don't rely as heavily on the hippocampus.
Source: Stress effects in the hippocampus, review
What Chronic Stress Does Differently
Animal research shows that chronic (rather than one-off) stress leads to measurable changes in the prefrontal cortex and hippocampus — regions that work together for both memory and attention — including reduced synaptic connectivity in some models. Human research on PTSD, an extreme example of chronic stress exposure, has found marked deficits in verbal recall tasks compared to non-traumatized individuals with similar backgrounds.
Source: Chronic stress and working memory, PMC6607320
Source: Cortisol-induced memory enhancement, PMC10601369
What Actually Helps
- Regular physical activity — one of the most consistently supported ways to blunt the cognitive impact of chronic stress
- Adequate sleep — stress and sleep loss compound each other's effects on the same brain regions
- A genuine outlet — structured breathing practice, time outdoors, or any activity that reliably brings your stress response back down, done consistently rather than only during acute stress
- Addressing the source where possible — chronic, unaddressed stressors tend to produce chronic effects; this isn't something willpower alone resolves
If stress feels unmanageable or is significantly affecting daily function, that's worth discussing with a doctor or therapist rather than working through alone.
Read: 10 Ways to Support Your Memory →