"Some of it is real and some of it is imagined on the part of the officers involved: fear, anxiety, wanting to do a better job," said Sanders, who consults with physicians across the country as director of the Police Stress Institute.
The temptation to find a "quick fix" is always present, said Sanders. Several older studies have placed police officers at the "bottom of the fitness scale," below firefighters and outranked by inmates, he said.
Typically, departments "turn a blind eye," to steroid use, according to Sanders.
The International Association of Police Chiefs Association did not return calls for comment, but at least one of those being investigated in the New York City probe is a high-ranking officer, according to local news reports.
"The body feels really comfortable and likes [the hormones]," said Sanders. "You feel better, feel more buff and feel more able to take on the bad people."
Indeed, Matthew felt the positive effects of steroids after only three months' use. His weight jumped from 170 pounds to 192 pounds, and he was able to bench-press 300 pounds from 225 pounds.
His habit — 500-700 milliliters a week injected into his deltoids, thighs or buttocks — cost about $500 a month.
"I was incredibly stronger," he said. "I never felt healthier in my life and woke up full of energy and felt it throughout the day. Never once did I feel out of control."
"Maybe I was a little edgier," he added. "The kids got me upset a little more and I was less tolerant, but never to the point where I would physically do anyone harm."
Still, said Sanders, steroid users tend to think "more is better" and don't know where to draw the line as they build bulk. Users typically combine steroids with a combination of drugs in a phenomenon known as "stacking," and "cycle" on and off the drugs to avoid building a tolerance.
"They can go from being calm and collected to raging bulls," said Sanders. "There is also a subcategory of these folks like the crazy Vietnam veteran. They think that if they appear crazy, people will back off."
But even short-term use of steroids can cause damage to brain tissue, which never grows back. And according to the National Institute of Drug Abuse, steroid abuse can cause internal organ damage, jaundice and high blood pressure.
Men can also experience testicle shrinkage and breast development. Women can see side effects of facial hair growth, menstrual changes and a deepened voice. Teenagers may stop growing.
Research shows extreme mood swings can occur as a result of taking steroids, leading to violence. Users may suffer irritability, delusions and impaired judgment.
"When they are used in excess, the individual crosses the line from adding muscle mass to rage or aggression or suicide," said Dr. Robert S. Gotlin, director of orthopaedic and sports rehabilitation at Beth Israel Medical Center in New York City. "Suppose that person is carrying a gun."
"The results are so profound, and it's so accessible," he said.
In Matthew's case, he obtained steroids from a friend. At least 10 other officers in his 75-member department were users when he started taking them. Steroids are readily accessible at gyms — "if you know the right people" and online, he said.