Early in my career, I wrote a paper titled “The Dementia Syndrome,” which was published in the British journal The Lancet.

I noted that dementia is a syndrome of mental symptoms and cognitive losses that impair functioning, and pointed out that many medical conditions can contribute to it.

This idea contradicted the common belief that Alzheimer’s disease was the only cause of dementia.

But I detailed so many causes of dementia that the reference list was almost as long as the paper itself.

The journal accepted the manuscript with one recommendation: Cut back on the references.

Just as dementia can have multiple medical causes, many medical conditions can present as psychological symptoms.

Examples of mental symptoms associated with physical ailments include:

• Psychosis (delusions, hallucinations). Stroke, brain tumor, steroid medication, substance abuse, epilepsy, fever, narcolepsy

• Depression. Low vitamin D, B12, or folic acid, hypothyroidism, head trauma, hormonal imbalances, diabetes, heart disease, some cancers and cancer drugs, Lyme disease, lupus, sleep disorders, Alzheimer’s disease

• Anxiety. Hyperthyroidism, low blood pressure, head trauma, respiratory diseases

• Irritability. Head trauma, temporal lobe epilepsy, Alzheimer’s, infections, hormonal imbalances

• Cognitive/memory impairments. Head trauma, meningitis, Alzheimer’s, Parkinson’s disease, liver failure, mercury or lead poisoning