Not long ago Dr. Rangan Chatterjee had a patient with Type 2 diabetes who was struggling to lower his blood sugar levels despite following an intense diet and exercise program.

Dr. Chatterjee counseled him to focus on the root cause of his problem: Chronic stress. The patient, a 53-year-old businessman, had been putting in long hours at the office, working late into the night and skimping on sleep. Dr. Chatterjee told him that constant stress can wreak havoc on blood sugar levels, and then urged him to practice yoga and meditation and to shut off his computer 90 minutes before bed each night. Six months later, the patient’s blood sugar levels had dramatically improved and were close to normal.

Dr. Chatterjee, an author, television host and influential British doctor, believes the role of stress in chronic disease is far too often overlooked. He estimates that 80 percent of the problems he sees in his clinic — conditions like high blood pressure, insomnia, depression, metabolic disease and weight gain — are in some way related to stress.

“A lot of people are oblivious to the effects of stress,” Dr. Chatterjee said.

Stress is of course an inevitable part of life, and in small doses it can be beneficial. But in recent years a growing body of research has shown that persistently high levels of social and emotional stress — the kind brought on by a high-pressure job, a divorce, financial worries or strained relationships, for example — can dampen the immune system and promote inflammation, heart disease and premature aging.