( CNN ) Here 's a roundup of five medical studies published this week that might give you new insights into your health . Remember , correlation is not causation -- so if a study finds a connection between two things , it does n't mean that one causes the other . Dream on and it 'll get weird . At the beginning of your sleep cycle , you may be dreaming about grocery shopping or your favorite TV show . But by the end of the night , you more likely will be dreaming about doing that shopping in your underwear with a murderous clown following you . In a study in the American Psychological Association journal , scientists followed the dream patterns of 16 people over two nights . The dreamers were awakened four times a night and asked to describe their dreams . The researchers found the longer someone slept the stranger and more emotional and in-depth their dreams got . Scientists concluded that a particular time of night may affect the content of dreams . A new way to detect depression . Currently , a doctor or social worker will ask you a standard set of questions to determine if you are depressed . Depression is often underdiagnosed because studies have shown patients frequently underreport their symptoms . Scientists at Northwestern University have come up with an alternative way to diagnose depression that uses a blood test , according to a study from Translational Psychiatry . The blood test looks at nine genetic markers in the blood that have been linked to depression . Scientists tried the test on 32 adults who were diagnosed as depressed and 32 who were not . After 18 weeks of therapy , those who were considered depressed were tested again . Those who improved through therapy showed a change in their genetic markers . The accuracy of the blood test showed similar results to people who were diagnosed through diagnostic interviews . Could a blood test predict suicides ? American beer bellies are getting bigger . Americans are getting bigger around the middle , according to a study in the Journal of the American Medical Association . That 's considered the most dangerous place on the body to gain weight . Studies have shown that people whose weight settles in their midsections have a higher risk for diabetes , heart disease and other serious conditions . In this study , the Centers for Disease Control and Prevention looked at adults over a period of 12 years . They found that the average waist size went up nearly an inch for men , to almost 40 inches . For women , the average waistline was about 38 inches , which is up nearly an inch and a half from 2000 . By the CDC 's estimates , 54 % of U.S. adults are heavier in their midsections . That 's up from 46 % in 1999-2000 . The average body mass index , or BMI , has stayed steady . Illicit drug use among teens is down slightly . Fewer teens are using illicit drugs and binge drinking , according to the National Survey on Drug Use and Health , which was released in full this week . About 8.8 % of teens 12 to 17 reported using illegal drugs in the survey , a decrease of 13 % from 2009 and 24 % from 2002 . Fewer teens also reported drinking in the month before completing the survey . Around 6.2 % reported binge drinking . Even marijuana use among teens was down slightly . Researchers did not see a change in the number of people over 12 who were using pain relievers for nonmedical purposes . Around 4.5 million Americans admitted to doing so , a rate similar to those in 2011 and 2012 . Gupta : How we created the heroin problem . A link between artificial sweeteners and diabetes . Artificial sweeteners may be messing with our gut bacteria and , in turn , with our ability to tolerate glucose . Glucose intolerance is a condition that can lead to diabetes . The series of studies appeared this week in the journal Nature . Scientists found that when mice ate or drank liquid or food made from aspartame , saccharin or sucralose , many of them became glucose intolerant . Researchers then tested the same thing out in seven human volunteers . Four of the seven developed glucose intolerance after consuming a regular dose of saccharin for a week . These individuals were not regular users of artificial sweeteners before the experiment . In a separate study of 400 humans , the scientists noticed the gut bacteria in study participants changed after they consumed artificial sweeteners . Gut bacteria are different in everyone . But some experts believe our gut bacteria can affect how our body processes food and burns calories . They theorize that the way sweeteners react with gut bacteria may affect whether someone gains or loses weight .
Average BMI has stayed the same for Americans , but our family size is increasing . New artificial hormones make some mice food intolerant , leading to diabetes . Teens are doing fewer illicit drugs , a national survey finds .