Love at the level of biology is all chemicals. The attraction process is strongly linked to physiological arousal that typically starts with increased heart rate and sweatiness. When you catch sight of your beloved, your heart starts racing because of an adrenaline rush.
The brain sends signals to the adrenal gland, which secretes hormones such as adrenaline, epinephrine and norepinephrine. They flow through the blood and cause the heart to beat faster and stronger. It is similar to a fast heartbeat while running on a treadmill. For people with serious heart problems, love could actually be dangerous because when the heart rate goes up, the heart uses more oxygen, which can be risky for a person with blood vessel blockages or who has had a prior heart attack. Good medicines such as beta blockers help curb the adrenaline response. The norepinephrine, a stress hormone that governs attention and responding actions, makes one feel weak in the knees. The brain imaging studies of people who said they were “madly in love” showed activity in the area of the brain that produces the neurotransmitter dopamine.
Dopamine and norepinephrine are closely related. Dopamine gives you focused attention, the craving, the euphoria, the energy and the motivation to win life’s greatest prize. This norepinephrine response seems to be more active in people who are in love. Serotonin system too plays a role. Data from an Italian study indicate that a drop in serotonin levels is associated with obsessive thinking. The stress hormone cortisol has also been shown to have implications for love. Those who are in love show an increase in stress hormones such as cortisol.
Three brain systems play vital role in romantic love: sex drive, love and attachment. The sex drive evolved to get you to look for a lot of partners, the “love” portion is for focusing mating energy on one specific person at a time, and attachment is for allowing you to tolerate the partner — at least, long enough to have children with him or her. These systems are often connected, but can function separately. You can start out with one of them — casual sex, or an intense feeling of love, or an emotional connection — and move on to the others. For example, what may start out as a one-night stand may feel like more because the hormones oxytocin and vasopressin, released during orgasm, make you feel deeply attached to someone. You may feel in love after that, or instead feel somehow responsible for the person, because of these hormones.
The romantic love doesn’t have to die. The activity level in the brains of people who are in love after 20 years of marriage is same as in people who had just fallen in love. This brain area makes dopamine and sends it to other areas. In the days of early humans, in hunting-and-gathering societies, these qualities were especially advantageous for finding a person to bear and raise children.
Love also has health benefits for people who have aged beyond their reproductive years. Being in love makes people feel optimistic, energetic, focused and motivated, which were all positive for health and societal contribution in the early days of humans. So, it makes sense evolutionarily that people can still fall in love after their childbearing period.
Romance is good for health. Studies have shown that people who have frequent sex are generally healthier, with a longer life, fewer coronary events and lower blood pressure. A 1995 study in the journal Demography found that marriage adds seven years to a man’s life and two years to a woman’s.
It is hypothesized that people for whom the love is still new will respond to the stress and recover from it quicker than those who have recently been in a breakup or have been in a relationship for a long time. The guess is that when individuals are falling in love, they are walking around with rose-colored glasses.