In brief

• The rate of prescription painkiller abuse among American teenagers is 40 percent higher than in previous generations, and it is now the second most common type of illegal drug use after marijuana, according to University of Colorado Denver researchers. In an analysis of data from the National Survey on Drug Use and Health from 1985 to 2009, scientists found that children born between 1980 and 1994 used painkillers such as vicodin, valium and oxycontin 40 percent more often than any other age group. This trend existed for both genders and across all racial and ethnic groups. The increasing availability of these drugs from parents' medicine cabinets may have been to blame, the researchers say. (Journal of Adolescent Health, online Oct. 16)

• Good parenting is more important to preventing teen drug use than good schools, according to a study conducted by scientists at North Carolina State University, Brigham Young University and Pennsylvania State University. The researchers evaluated data from a nationally representative study that collected social capital information about adult investment in children at home and school — factors such as parent-child bonds and teacher-student relationships — and drug and alcohol use from more than 10,000 students and their parents, teachers and school administrators. They found that students with high levels of family social capital and low levels of school social capital were less likely to use marijuana or alcohol than students with high levels of school social capital but low family social capital. (Journal of Drug Issues, online Nov. 8)

• People are more motivated to perform mundane tasks if they think they're getting a variety of rewards, according to research led by a scientist at the University of Southern California. Across six experiments with 737 people, researchers tested the effects of different, arbitrary categories of rewards — for example, prizes of equal value in different colored boxes — on people's motivation to complete a task such as transcribing a typewritten text or alphabetizing pictures of fruit. People who got to choose two rewards from different categories worked longer and harder on the task than those who could choose the same number of non-categorized rewards. (Journal of Personality and Social Psychology, online Nov. 26)

• Being a good partner may make you a better parent, according to research from the University of Bristol. Looking at 125 couples with children ages 7 to 8, the study examined the way the couples were attached to each other, the parenting styles they used with their children and their capacity to tune in to their partners' needs. The researchers found that the same set of skills underpins caregiving across different types of relationships, and for both mothers and fathers. Surprisingly, the researchers found that how the subjects cared for their partners did not relate to how their partners behaved as parents. (Personality and Social Psychology Bulletin, online Dec. 6)

• In both rich and poor countries, the average person's happiness is based on a combination of individual wealth, possessions and optimism, according to an analysis of a new Gallup World Poll led by a University of Illinois psychologist. Based on responses from more than 800,000 people in 135 countries from 2005 to 2011, researchers found that higher income does lead to happiness but that it depends on people's ability to be optimistic, not have high aspirations and be able to afford more. (Journal of Personality and Social Psychology, online Oct. 29)

• Black women who were abused as children are more likely to experience adult-onset asthma compared with black women who experienced no child abuse, according to a Boston University study. Researchers followed more than 28,000 black women from 1995 to 2011 and found that the incidence of adult-onset asthma was more than 20 percent higher among women who had been abused as children. There was little evidence, however, that abuse during adolescence was associated with a greater risk for adult-onset asthma. (Journal of Allergy and Clinical Immunology, online Dec. 7)

• The way we read words changes as we age, according to a study from the University of Leicester in England. The researchers used eye-tracking software to measure the eye movements of younger and older adults to determine how well they read blurry or sharp lines of text. They found that people ages 18 to 30 more easily read text with fine visual detail, whereas adults over 65 found it more difficult. However, the older adult group found it easier to read more blurred text, and they comprehended all the text as accurately as the younger readers — findings that support the view that older adults use different reading strategies than younger adults and that they rely more on holistic cues than individual letters. (Psychology and Aging, online Oct. 15)

• Fetuses yawn in the womb, according to ultrasound scans of 15 healthy fetuses, completed at Durham and Lancaster Universities. The study distinguished yawning from non-yawn mouth opening based on the duration of the mouth opening and classified more than half of the mouth openings in the study as yawns. While the function and importance of yawning are still unknown, the study's findings suggest that yawning could relate to central nervous system maturation. (PLoS ONE, Nov. 21)

• Even a little exercise can go a long way toward extending life, regardless of weight, find National Cancer Institute researchers. They analyzed data on more than 650,000 adults age 40 and older who were followed for about 10 years. They found that people who walked briskly or engaged in some other physical activity for 45 minutes a week — half the recommended amount — gained nearly two years in life expectancy compared with inactive people. Those who exercised even more gained up to four and a half years of life. (PLoS Medicine, November)

• Adults with attention deficit hyperactivity disorder commit fewer crimes when on medication, according to a study conducted at the Karolinska Institute in Sweden. Researchers studied data from more than 25,000 people with ADHD over a four-year period and found that the incidence of criminal behavior was lower among those taking Adderall, Ritalin and other anti-ADHD medication. Additionally, individual participants were 32 percent less likely to commit a crime when taking drugs than when on a break from medication. (New England Journal of Medicine, Nov. 22)

• Even moderate drinking in pregnancy can affect a child's IQ, finds a study led by researchers from the universities of Bristol and Oxford. More than 4,000 women in the United Kingdom provided information about their alcohol intake during pregnancy. Their children's IQ was tested at age 8. The researchers found that four variations in alcohol-metabolizing genes in the children were strongly related to lower IQ: On average, a child's IQ was almost two points lower for each of the four genetic variants they had. This effect, however, was seen only among children of women who were moderate drinkers — consuming one to six drinks a week — during pregnancy. There was no effect evident among children whose mothers abstained during pregnancy; heavy drinkers were not included in the study. (PLoS ONE, Nov. 14)

• People identify symptoms of depression more readily in women than men, according to research conducted at the University of Westminster. In the study, the researcher presented 1,218 participants — recruited via direct approach in public locations in three cities in Britain — with descriptions of one of two fictitious subjects, Kate and Jack, who both reported identical symptoms of major depression. Participants were then asked to identify whether Kate or Jack suffered a mental health disorder, and how likely they would be to recommend that the subject seek professional help. Both men and women were equally likely to classify Kate as having a mental health disorder, but men were less likely than women to indicate that Jack suffered from depression. Respondents, particularly men, rated Kate's case as significantly more distressing, difficult to treat and deserving of sympathy than they did Jack's case. (PLoS ONE, Nov. 14)

• Men born without a sense of smell find fewer sexual partners than other men, and women with the same disorder feel more insecure in their relationships, according to a study led by a psychologist at the University of Gothenburg in Sweden. While "smelling" men reported an average of nine sexual partners over their lifetime, men born without a sense of smell — a condition known as anosmia — reported having three. Anosmic women reported no fewer partners than controls, but they reported being more insecure in their relationships. Lacking a sense of smell may cause people to miss important social cues, resulting in relationship difficulties, the researchers suggest. (Biological Psychology, online Nov. 22)

• Older people tend to miss cues that a person is not trustworthy, finds a study led by psychologists at the University of California, Los Angeles. Researchers asked 119 older adults, ages 55 to 84, and 24 younger adults between the ages of 20 and 42 to rate people in photographs as trustworthy, neutral or untrustworthy. Older adults were equally proficient at identifying people judged to be trustworthy or neutral but much more likely to miss signs of those who may be untrustworthy — such as insincere smiles, averted gazes and postures that leaned away rather than toward the camera — and to view suspicious-looking people as approachable. (Proceedings of the National Academy of Sciences, online Oct. 24)

• Brain changes in children who have sustained a concussion persist for months after the symptoms of the injury are gone, finds a study from the University of New Mexico. Researchers conducted cognitive testing and used diffusion tensor imaging (DTI) to examine the brains of 15 children who had recently experienced a concussion and 15 unaffected children. Immediately after their accidents, children with concussions showed subtle cognitive deficits and disruptions in brain connectivity compared with their healthy counterparts. During a follow-up visit four months later, DTI revealed that the structural changes to the brain remained, even after cognitive deficits had improved. (The Journal of Neuroscience, Dec. 12)

—Amy Novotney