Acne has long been known to cause stress. Now, a new study offers evidence that what has long been suspected — that stress causes acne — may also be true.

Researchers at Stanford put the question to the test by examining students with acne problems on two occasions: once during a relatively stress-free time and again during an exam period. They also administered standardized questionnaires intended to assess stress levels.

The researchers, whose report appears in The Archives of Dermatology, found that ”changes in acne severity correlate highly with increasing stress.”

For people who use acne medicine, the lesson may be to pay close attention to what is going on in their lives, said the senior researcher, Dr. Alexa B. Kimball.

”If they know that a stressful time is coming up,” Dr. Kimball said, ”that’s an important time to be particularly compliant with their medicine.”

Doctors treating acne patients may also want to take stressful conditions into account in deciding when to time a change in prescription, she said.

The findings are based on a study of 22 students — 15 men and 7 women — with serious acne problems. Acne affects 85 percent of the population at some point in life.

Why stress may cause the skin to erupt is unclear. Some research suggests that it may provoke a greater release of hormones associated with acne. The researchers also looked at whether changes in people’s daily lives — in sleep, for example, or eating habits — played a role. Even when these were factored out, the study said, the students’ acne became worse.

The role of stress in acne should not be surprising, Dr. Kimball said. She noted that some acne patients responded well to biofeedback, which is intended to reduce stress. Stress has also been linked to numerous other medical problems and has been shown to affect wound healing.

Q: My teenage son has acne and I just picked up his Accutane (isotretinoin) from the pharmacy. I’ve been reading on the Internet about it, and now I’m worried about starting him on it. His skin isn’t that bad. Can it really cause suicide?

- K.S. in

Tulsa, Okla.

A: Possibly, but so many factors contribute to suicide, you can’t exclusively blame a drug in every case. Still, the devastation to families affected by this medication can be horrific.

Some drugs can cause psychosis, as evidenced by seeing or hearing things that aren’t really there, behaving strangely and experiencing paranoia or delusional thinking.

Accutane and its generic, isotretinoin, can alter mood, and the manufacturer, Roche, openly shares this information. Other brand names include Amnesteem, Claravis and Sotret. These drugs, synthetic derivatives of vitamin A, can negatively impact brain chemicals such as dopamine and serotonin. An Accutane package insert warns of: “depression, psychosis and rarely, suicidal ideation, suicide attempts and suicide.”

Statistics show that between 1989 and 2003, there were 216 reported drug-linked suicides among U.S. teens younger than 18. Of these, 72 suicides were linked to Accutane (isotretinoin). The next highest number of suicides in that time period - 55 - involved Prozac (fluoxetine).

The FDA Web site warns: “All patients treated with isotretinoin should be observed closely for symptoms of depression or suicidal thoughts, such as sad mood, irritability, acting on dangerous impulses, anger, loss of pleasure … mood disturbance, psychosis, or aggression.”

Psychiatric side effects tied to vitamin A are nothing new. As early as 1856, the Arctic explorer Elisha Kane noted psychiatric symptoms in men who ate polar bear liver, later found to contain large amounts of vitamin A. In the last 150 years, case reports of psychosis, schizophrenia and suicide associated with too much vitamin A and vitamin A-derived pharmaceutical drugs have increased substantially.

Parents deserve to know everything about isotretinoin (and all drugs) because their children’s lives may depend on how well they are informed.

Even if your child is off isotretinoin, keep watching him closely because adverse effects may occur several months after discontinuation. Remember, stopping a drug that alters brain chemicals does not mean the brain chemicals magically become balanced again.

Last warning: Isotretinoin-type drugs cause birth defects and are not often prescribed for sexually active women of childbearing age. And no one should ever share this medication with friends.

Suzy Cohen is a registered pharmacist. To contact her, visit http://www.dearpharmacist.com.

If I want to simplify my beauty routine, or for other reasons, I sometimes mix my products together. For example, I will mix 10 percent benzoyl peroxide gel with my moisturizer for a 2.5 percent anti-acne medication. Or I add a couple drops of pure salicylic acid to a benzoyl peroxide product. Occasionally, I add an oil-absorbing mask to my sunscreen or to my nighttime moisturizer if I want to control oil, or I add a couple drops of glycerin if I find a product is too drying.

Can I do that? I mean, can salicylic acid and benzoyl peroxide coexist in one product? Does adding something to sunscreen mess up its protection? Can that be counteracted by adding a squirt of, say, a sunscreen with SPF 50? If a toner had a good pH, and I added a couple drops of salicylic acid, would it still be stable? I haven’t tried all of these yet, but am quite enjoying being a cosmetic chemist in my own bathroom.

A: Although I admire your ingenuity in thinking about cosmetics, I must advise that what you’re doing is indeed affecting the stability, performance and safety of the products you’re experimenting with. The answer to the question of “Can I do that?” is yes, of course you can - but it doesn’t mean you should. Cosmetics chemistry is as much art as it is science. Adding ingredients to finished products in an effort to create an enhanced version or to alter the original function won’t necessarily blow up in your face, but you are negating the effectiveness of the very ingredients that could be helping your skin.

For example, salicylic acid (BHA) must be in a base that has a certain pH range if it is going to exfoliate skin. Mixing it into a product with a pH above that range will not produce the results you’re looking for, and may cause undue irritation. According to the chemists I spoke to, salicylic acid and benzoyl peroxide don’t coexist well in the same product, because they need different pH ranges for optimal effectiveness. In addition, the FDA does not permit both active ingredients in one product, which explains why no company is making a BHA/benzoyl peroxide solution (Source: Code of Federal Regulations, Title 21, Volume 5, April 1).

Milk of magnesia is an effective absorbent for excess oil, but adding it to a moisturizer defeats the purpose because it also “absorbs” the oil-soluble ingredients in the moisturizer, which in turn reduces its oil-absorbing ability on your skin.

As for adding ingredients to sunscreens, yes, doing so will disrupt the level of protection it was designed to supply (in fact, when a manufacturer changes even one ingredient in a sunscreen formula the FDA mandates retesting it from scratch).

The only type of mixing that can work safely and be of benefit is when you have a need for a more emollient moisturizer, especially during winter or in arid environments. In that case, it is fine to add a few drops of glycerin, olive or jojoba oil, to your regular moisturizer. However, to avoid affecting the stability of the ingredients in the entire container of product, be sure to do the mixing in your hand, or apply the oil over the moisturizer directly onto your skin.

A powerful and popular acne drug whose use is already closely monitored because it can cause serious birth defects triggers higher levels of cholesterol and liver enzymes than previously reported, according to a study released yesterday.

The drug, isotretinoin, commonly marketed as Accutane, is a prescription treatment for severe acne, but is also known to have dangerous side effects, including depression and vision problems.

The study, published in the August issue of the Archives of Dermatology, assessed the frequency of abnormal laboratory blood tests in 13,772 people ages 13 to 50 who underwent isotretinoin treatment between 1995 and 2002.

Researchers analyzed medical records for each patient before, during and after they took the drug using information from laboratory blood tests of triglycerides, total cholesterol and liver enzyme levels.

Among patients with normal pretreatment laboratory tests, the study reported that 44 percent developed high triglycerides, 31 percent high cholesterol and 11 percent high liver enzymes while on the medicine. Lead author Dr. Lee T. Zane of the University of California at San Francisco said that previous observational studies found elevated triglycerides in the 5 to 18 percent range and elevated total cholesterol from 6 to 32 percent.

The seven-year study did not examine actual clinical outcomes for patients in the study and could not say what the elevated levels would mean over the long haul.

“Having abnormal test results does not necessarily signal the presence of a bad medical outcome,” said Zane, assistant professor of clinical dermatology. “Having elevated levels over a few months doesn’t guarantee a heart attack. It doesn’t promise liver failure. Physicians have carefully and successfully been monitoring this medicine for decades.”

Zane characterized Accutane as the “most important medication in dermatology in the last 30 years.”

“All this focus on the risks and we can lose sight of the benefits,” Zane said.

But Dr. Mark Avram, chief of dermatology at Long Island College Hospital in Brooklyn, said the study reinforced the need to remain guarded.

“Most people who take Accutane have no problem with it at all if you follow the protocol,” Avram said.

“But most people don’t take Accutane because it does have risks. But severe acne has a devastating affect on self-esteem and how a person functions. With isotretinoin, you need to be smart while you are on it.”

Shelley Rosenstock, a spokeswoman for the drug maker, Roche Laboratories Inc., said in a statement that the study findings were consistent with product information included with the drug since its approval in 1982.

“Prescribers have been advised to monitor these levels in laboratory tests … during treatment until the patient’s lipid response has been established (usually within four weeks), and consider the risk/benefit for patients for whom elevated lipid levels present a high risk,” Rosenstock stated.

In March, the Food and Drug Administration approved the manufacturer’s switch to the iPLEDGE online management program to reduce the risk of fetal exposure to the drug. To qualify for the drug, all female users, whether sexually active or not, are required to take two pregnancy tests and pledge to use two forms of birth control.