Newswise — In honor of Valentine's day, two articles in the February issue of the Harvard Health Letter look into some scientific questions on the nature of love.

The first discusses several theories about the biological basis behind falling in love. The newest theory finds a surprising similarity between love and such emotions as anxiety and fear. Researchers from University of Pisa measured hormone levels in 24 young people who reported recently falling in love. They found that the lovers had higher levels of the stress hormone cortisol than people who hadn't lately been bitten by the love bug. They also found that the men who were in love had less testosterone than their single counterparts, and the women in love had more. The researchers speculated that falling in love may reduce some of the differences between the sexes, making men softer and women more aggressive.

The second article discusses the phenomenon that people find others more attractive if they have meaningless things in common — like the same birthday or first initial. A 2004 paper on this subject noted that studies of phone listings revealed that people are more likely to marry others with similar names (Charlotte and Charlie, for example) than would be explained by chance. Another study found that subjects rated other people more attractive when a "code number" for that person was switched to match the subject's own birthday. Why would this be? The Harvard Health Letter says experts chalk it up to implicit egotism — we automatically think positively about people who remind us of ourselves, even if the reminder is trivial.

Also in this issue:

"¢ A new pill combining Zocor and Zetia for lowering cholesterol"¢ Seven tips for dry mouth"¢ The hormone DHEA for weight loss: Promising, but research is preliminary"¢ Can echinacea cure the common cold?"¢ Harvard Health Letter Editor in Chief Dr. Anthony Komaroff answers readers' questions about eating grapefruit while on Lipitor and screenings for brain aneurysms.

The Harvard Health Letter is available from Harvard Health Publications, the publishing division of Harvard Medical School. Subscribe at http://www.health.harvard.edu/health or by calling 1-877-649-9457 (toll free).