Why Houston is so sad this summer

Seasonal affective disorder (SAD) is a type of depression that usually occurs when days get short and dark in autumn and winter — but there's a summer version of it too.

Why it matters: Summer SAD could become a growing problem as heat persists and climate change worsens, Dr. Asim Shah, executive vice chair in the Menninger Department of Psychiatry and Behavioral Sciences at Houston's Baylor College of Medicine, tells Axios.

• The heat in Houston has broken records this summer, with little relief in sight.

The intrigue: Recent studies have shown a correlation between heat and suicide rates and mental health ER visits, per Texas Monthly.

• Disrupted sleep is one explanation for the link between heat and mental illness. Sleeping in a warm room for days or weeks can exacerbate health problems, including psychiatric disorders, per the New York Times.

What they're saying: "This year, [summer SAD] is more prevalent because of the severe heat we've had," Shah says. "We're having a new surge of some sort of similar seasonal affective disorder."

Of note: Shah recommends taking trips to cooler climates for a break, keeping cool by swimming, and ensuring your electrolytes are replenished.

Flashback: Norman Rosenthal, a clinical professor of psychiatry at Georgetown University School of Medicine, first identified SAD in 1984, he tells Axios.

• Patients felt lethargic in cold climates or rooms with little sunlight and gained weight.

• He gave the disorder its name and developed light therapy as a treatment.
• By 1989, he had identified summer SAD as a disorder.

Between the lines: Other researchers have since recognized SAD and conducted additional studies, but summer SAD is still not as widely researched as winter SAD.

What's next: Rosenthal's new book, "Defeating SAD," published this month, has a chapter about the disorder in summer, which dovetails with anxiety about climate change.

• "Hardly anybody really likes the intense heat. But as the summers get worse and worse, we begin to dread it," Rosenthal says.