A new study suggests that having sex more often does not make relationships happier, but rather leads to a slight decrease in their sexual desire and happiness level.

Earlier studies claimed that couples who have more sex are happier than those who do it less often. This idea became the subject of the study conducted by researchers from Carnegie Mellon University who involved 128 couples in a three-month period.

The couples were randomly assigned to two groups. One group was instructed to double the frequency of sex while the other received no instruction. The participants completed an online survey asking details about their frequency of sex, sexual enjoyment and happiness level at the beginning of the study. After three months, they completed another survey to see if there were any changes in the happiness level, especially for those who had more sex.

The analysis showed that those who were asked to increase their sex frequency reported a decrease in their sexual desire and enjoyment level. However, the researchers admitted that the study needs to be repeated because the couples seemed force to have sex more often instead of voluntarily initiating sex.

The researchers believe that their findings can help couples improve their sex lives and happiness. While they weren't able to prove that having more sex increases happiness, they still believe that it makes relationships healthier.

"The desire to have sex decreases much more quickly than the enjoyment of sex once it's been initiated. Instead of focusing on increasing sexual frequency to the levels they experienced at the beginning of a relationship, couples may want to work on creating an environment that sparks their desire and makes the sex that they do have even more fun," Tamar Krishnamurti, study co-author and a research scientist in CMU's Department of Engineering and Public Policy, said in a press release. 

The study was published in the May 8 issue of the Journal of Economic Behavior & Organization.