SATURDAY, July 31 (HealthDay News) -- When the days grow longer in the spring, teens experience hormonal changes that lead to later bedtimes and associated problems, such as lack of sleep and mood changes, researchers have found.

SATURDAY, July 31 (HealthDay News) -- Heat cramps, heat exhaustion and potentially fatal heat stroke are risks when exercising or playing sports during the summer, but they can be prevented by taking a few simple precautions, advises a Medical College of Georgia expert.

FRIDAY, July 30 (HealthDay News) -- A recent survey highlights the need for a horse rider safety, according to a University of Kentucky expert.

FRIDAY, July 30 (HealthDay News) -- Because of the freedom of movement it offered, the neck may have been a major contributor to the evolution of the human brain, according to researchers who compared human and fish genetics.

FRIDAY, July 30 (HealthDay News) -- The annual flu vaccine for the 2010-2011 influenza season has been approved by the U.S. Food and Drug Administration, the agency said Friday.

FRIDAY, July 30 (HealthDay News) -- The flu vaccines approved for the 2010-11 season protect against three strains of influenza, including the 2009 H1N1 pandemic swine flu strain, the U.S. Food and Drug Administration announced Friday.

FRIDAY, July 30 (HealthDay News) -- Patients with knee or hip osteoarthritis fare better if they continue to do their physical therapy exercises after completing a supervised exercise therapy at a medical facility, new research indicates.

FRIDAY, July 30 (HealthDay News) -- Health campaigns that highlight the problem of low screening rates for prostate cancer to promote such screenings seem to have an unintended effect: They discourage men from undergoing a prostate exam, a new German study suggests.

FRIDAY, July 30 (HealthDay News) -- The risk for childhood obesity may begin even before a child is born, say researchers who found that women who are overweight or obese before becoming pregnant are more likely to have overweight or obese toddlers and preschoolers.

FRIDAY, July 30 (HealthDay News) -- Two more cases of dengue fever were reported by health officials in Florida this week, bringing the total to 46 confirmed cases since last September, but a top government health official said it's too early to say whether the mosquito-borne tropical disease is gaining a foothold in the United States.

FRIDAY, July 30 (HealthDay News) -- Two more cases of dengue fever were reported by health officials in Florida this week, bringing the total to 46 confirmed cases since last September, but a top government health official said it's too early to say whether the mosquito-borne tropical disease is gaining a foothold in the United States.

FRIDAY, July 30 (HealthDay News) -- Genetics may determine to what extent you're swayed by the alcohol consumption of people around you, new research suggests.

FRIDAY, July 30 (HealthDay News) -- Contrave, an experimental weight loss drug that combines an antidepressant with an anti-addiction medication, appears to help users shed pounds when taken along with a healthy diet and exercise, researchers report.

FRIDAY, July 30 (HealthDay News) -- Swimmers who dip into the pollution-free waters of sub-tropical beaches, such as those in southern Florida, face an elevated risk for developing gastrointestinal and/or respiratory illnesses, a new study indicates.

(HealthDay News) -- Here are the latest clinical trials, courtesy of ClinicalConnection.com:

Here are some of the latest health and medical news developments, compiled by the editors of HealthDay: