Cortisol, memory and brain fog: what is known and when to see a clinician

Cortisol and thinking are linked in some well-documented conditions and in lab studies. For most people with a foggy head, though, the sources we use don’t point to cortisol as the reason. This page covers what the research does and doesn’t show.

What cortisol does to memory in healthy people

A 2023 review of the research describes the findings as mixed (Front Endocrinol, 2023). A few examples from it:

• Some studies found an inverted U-shaped pattern: memory retrieval did best at a middle cortisol level and worse at low or high levels. In one study the effect came from giving cortisol by injection in several doses, and it appeared within minutes.
• Age may matter. The review says younger people may be less vulnerable to cortisol’s effect on memory than older people.
• Results depend on when memory is tested, how aroused the person is and which brain region the task relies on.
• In one study, higher waking cortisol went with better working memory. Others link high cortisol with poorer memory, learning and attention in older adults.

The review’s own warning matters most for a reader with a test result in hand. It says a single morning cortisol sample gives very limited information about the daily pattern. One number says little, and it says nothing about your memory in particular.

Cushing’s syndrome and thinking

NIDDK lists “memory loss or trouble concentrating” among the health problems Cushing’s syndrome can cause, along with depression or other mood changes. The 2023 review adds that Cushing’s syndrome has been linked to cognitive symptoms and to brain changes, including smaller hippocampal volumes (the hippocampus is a region involved in memory). It reports that the brain changes are partly reversible after treatment, but that some people with Cushing’s disease still have problems with attention, memory and executive function after long-term remission.

How common the problems are depends on the source. The review, passing on figures from an earlier paper, puts memory impairment at about 83 percent of cases and reduced concentration at about 66 percent. In a 2019 questionnaire of 320 people with Cushing’s syndrome, 41.9 percent said memory problems and 45.0 percent said loss of concentration were among the symptoms they first noticed. After treatment, 33.8 percent still reported memory problems and 35.9 percent poor concentration (Endocrine Connections, 2022). That survey was online, mostly women, and its remission status was self-reported, so treat the figures as rough.

These numbers describe people who already have the condition. They don’t tell you how likely it is that your brain fog comes from it.

Low cortisol and thinking

NIDDK lists irritability and depression among the symptoms of adrenal insufficiency, alongside fatigue, muscle weakness, loss of appetite and weight loss. The 2023 review says the mental side of Addison’s disease is less well understood and that, on occasion, psychiatric or behavioral symptoms can be the only sign of an adrenal crisis. That’s uncommon. Vomiting you can’t stop, severe weakness and fainting are the signs to treat as urgent. See adrenal crisis.

What else causes brain fog

The sources we use don’t define brain fog. They list memory loss and trouble concentrating, and give plenty of other causes.

• Stress. MedlinePlus lists difficulty focusing your thoughts among the symptoms to get help for if they last two weeks or more.
• Mood, medicines and other conditions. MedlinePlus lists depression, kidney, liver or thyroid problems and reactions to certain medicines among the possible causes of forgetfulness that goes beyond the occasional lapse. See cortisol and sleep and cortisol and anxiety.
• Tiredness. Long-lasting fatigue has its own list of causes. See cortisol and fatigue.

A cortisol test is not a brain fog test. MedlinePlus says a cortisol test alone can’t diagnose the cause of an abnormal level, and the test can’t diagnose or rule out Cushing’s syndrome or adrenal insufficiency by itself.

When to see a clinician

• Forgetfulness worries you, or others notice it. MedlinePlus says to see your provider if you’re worried. That’s the right first step whatever the cause.
• Brain fog comes with other signs. For high cortisol, NIDDK lists weight gain, a round face, easy bruising, wide purple stretch marks, weak muscles and high blood pressure. For low cortisol, it lists long-lasting fatigue, weight loss and dizziness when standing. See effects of high cortisol and low cortisol symptoms.
• You take a steroid medicine. Tell the prescriber about any change in thinking or mood. Don’t stop or change the medicine yourself.

MedlinePlus says to get help if severe symptoms such as difficulty focusing last two weeks or more, and to get help right away if stress is leading to thoughts of suicide or a feeling that you can’t cope.

Keep reading

• Effects of high cortisol

  What long-term high cortisol can do and how it is worked up.

• Cortisol and sleep

  How sleep and cortisol relate, and what the studies show.

• Cortisol and anxiety

  What is known and not known about anxiety and cortisol.

• Cortisol and fatigue

  When tiredness is and isn't about cortisol.