Alzheimer’s isn’t the only condition that harms your memory. These four problems can also leave you feeling foggy.

Depression
People battling the blues have lower levels of serotonin and norepinephrine—two neurotransmitters that help boost attention and alertness, explains Majid Fotuhi, MD, chair of the Memosyn Neurology Institute and author of Boost Your Brain ($20, amazon.com). The disease is also linked to a smaller hippocampus, according to a 2004 Danish review.

Other symptoms: Fatigue, irritability, trouble sleeping, feeling hopeless, under- or overeating (lasting more than two weeks).

Rx: Your MD will refer you to a psychologist or psychiatrist for counseling and possibly meds.

RELATED: 10 Signs You Should See a Doctor for Depression

Hypothyroidism
Your thyroid hormones control your metabolism, and if they’re low, it may take longer for nutrients to reach your brain.

Other symptoms: Weight gain, fatigue, dry skin, hair loss, feeling cold.

Rx: Your doc may prescribe synthetic thyroid hormone.

RELATED: 12 Unexpected Things That Mess With Your Memory

Sleep apnea
“When women in their 40s come to my office complaining of memory issues, one of the most common causes is sleep apnea,” said Dr. James Leverenz, Cleveland director of the Lou Ruvo Center for Brain Health at the Cleveland Clinic. The condition causes a closing or narrowing of the airway passages, which can lower oxygen levels in the brain.

Other symptoms: Snoring, gasping, waking up exhausted, morning headaches, daytime sleepiness.

Rx: Remedies include losing weight, avoiding alcohol and possibly using a CPAP machine to keep your airway open with a stream of air.

RELATED: 7 Tricks to Improve Your Memory

Celiac disease
Researchers aren’t sure how this autoimmune disorder might affect memory, but one theory is that, left untreated, the disease may cause systemic inflammation that can have a negative effect on the brain.

Other symptoms: Fatigue, joint pain, migraines, possibly an itchy skin rash, diarrhea (in about a third of adult cases).

Rx: A small 2014 Australian study found that when celiac patients followed a gluten-free diet, brain-fog symptoms improved within a year.

This article originally appeared on Health.com.