This month’s terrorist bombing attacks in London have ratcheted up already-high tension levels of New York City police officers.

Professionals in law enforcement, psychiatry, and academe said the London attacks added another layer of stress to the job and for some officers triggered long-buried memories of the 2001 terrorist attacks. As a result, many police officers find themselves perpetually in an intensified – and exhausting – state of alertness.

“A lot of guys in Midtown are on edge,” a recently retired police sergeant and former commanding officer of the Manhattan Robbery Squad, Gerard Kane, said of his former colleagues. “They’re waiting for a suicide bomber.”

He said feelings of tension subside the farther away the police officers work from Midtown.

“They all have it in their mind, is New York going to be next?” a psychiatrist who specializes in treating police officers, Frank Dowling, said.

These days, he said, officers experience a “medium level” of stress “all the time.”

“At the very least it’s fatiguing,” Dr. Dowling said. “Now you can’t even turn it down and get a break between incidents.”

Terrorist strikes compound the already considerable pressures of the job, particularly for stress-prone officers, according to a professor of law and police science at Manhattan’s John Jay College of Criminal Justice, Eli Silverman.

“You’re responsible for more,” he said. Not only must police officers continue pursuing criminals, but since the September 11, 2001, attacks they must also be on constant lookout for terrorists.

Police work is an anxiety-provoking job on an ordinary day, with its varying shifts and the exposure to violence. “Imagine if you had hundreds of those incidents over a 20-year career,” Dr. Dowling said. “The problem is the cumulative effect.”

Add to that the fact that “the public hates police officers except for the six months after 9/11,” he said.

In “Policing: An International Journal of Police Strategies & Management,” a 2000 article about alcohol use among police officers in Australia said: “Policing has been classified as a high stress occupation, with up to 47 percent of officers in self-report studies citing stress as a significant consequence of the job. Epidemiological evidence in the form of high rates of heart disease, mental health problems, divorce, and suicide, as well as alcoholism and drug abuse, seems to support this.”

About one-third of police officers develop a stress-related problem requiring professional assistance by the end of their 20-year career, Dr. Dowling said. He estimated that excessive drinking affects between 20% and 25% of police officers, roughly twice the rate of the general population. Drinking is the norm in police culture, although not as much today as it was a couple of decades ago, some police officers said. The divorce rate is higher for law enforcers, with some research indicating that between 70% and 80% of police officers will get divorced while on the job. Also, police officers, compared to the population at large, have roughly double the rate of suicide, according to Dr. Dowling.

Although police culture still depends on officers’ suppressing negative emotions, more and more police officers have sought help for emotional problems. To meet that need, the independent organization Police Organization Providing Peer Assistance was developed in 1996. A 31-year veteran of the Police Department, Bill Genet, founded the nonprofit organization in 1995 in response to a particularly high suicide rate among officers in 1994 and 1995, 12 and then 14. The program provides peer counseling to police officers experiencing personal or professional difficulties. Its hotline receives four times as many calls now as it did at its inception, according to Mr. Genet.

Some academic analysts said stress problems are endemic to police departments.The New York department has a counseling arm, but many officers fear their problems will be reported to department officials.

Also, seeking help for coping with stress still carries a stigma, according to the chairwoman of the law and police science department at John Jay, Maki Haberfeld, who is author of the book “Critical Issues in Police Training.” She said stress management in policing is still “highly undeveloped.”

Police administrators should require stress-management training in the Police Academy for cadets and in annual sessions for officers, she said.

“It’s definitely a huge problem within the police profession, and it is overlooked by 99% of police departments around the country,” the professor said.

Many police officers decline to be interviewed on any subject, citing department policy, and those who would consent to discuss stress-related problems requested anonymity, in part because of the issue’s sensitivity and the personal anonymity observed by organizations such as Alcoholics Anonymous.

One 25-year veteran police officer, who asked to remain anonymous, said he found himself feeling suicidal and in the grips of alcoholism more than 18 years ago before getting sober through AA. Job stress, the officer said, contributed to an already budding addiction to alcohol. Even today, he said, there are the long hours, disrupting an officer’s personal life; the diet of rapidly consumed fast food; the “insane demands,” and the “nonstop” pace of the work.

In a given workday, police officers shift gears from sedentary to a sudden flurry of activity. “You get your heart up there, through the roof, a couple of times a night,” the police officer said.

Other factors that commonly contribute to the amount of stress, Mr. Silverman from John Jay said, include inadequate pay, the perception that promotions are based on favoritism, and the return of convicted perpetrators to the streets.

A police officer for 12 years, who also requested anonymity, said police work “puts a strain on your marriage.” In particular, he said, the unpredictable hours make it “very difficult to plan family events with the job.” The officer said he drank heavily because of job related stress and other factors before achieving sobriety more than three years ago.