Many songs, poems, and books have been written on love's strong effect on people. The state of being in love has even been compared to being sick or mad. A study by Professor Semir Zeki of University College London has found that love does affect people's brains by making them feel great. Zeki studied young men and women who had recently fallen in love. He found that, when they were looking at photos of their loved ones, there was heightened activity in four areas of their brains. These areas deal with emotions, and one of them, in particular, is known to respond to drugs that cause feelings of great joy and excitement. Interestingly, the study also found a lack of activity in two other areas of the brain when the volunteers looked at their lovers' photographs. One of these areas is linked to feelings of sadness, while the other is often active in people suffering from depression. It seems love really can be _ . The state of being in love, according to some scientists, may actually be good for your health. Although scientists know that being in love can make a person feel great, the exact influence of love on a person's health is harder to determine. However, scientists say that people do need love in order to live healthy lives. According to Dr. Thomas Lewis, people need to be in relationships because that is how we are designed. He says the brain can only maintain  the overall stability of a person's immune  system, bodily rhythms, and heart if it receives input  from outside the body in the form of emotional connections with others. Professor Antonio Damasio has a similar view. He says that love enriches a person's imagination and creativity, and makes a person's body work better. He also believes that love can even improve the body's ability to fight against disease. Damasio's wise words of advice are " Choose love and you will live longer." The main idea of this passage is   _  .
love can really cause people active love has effect on songs and books love is linked with emotion love is what we need