Is love a marathon or a sprint? For your brain, it’s both.

Most of us are familiar with the rush associated with ‘falling in love’. Sweaty palms, a racing heart, a little bit of a swoon every time your new love looks at you, and a tendency to overhaul the other things going on in your life to maximize the time you spend with that individual. But as many of us also know, that feeling doesn’t last. Sometimes it fades entirely and the person who used to be your sun and stars is more like your ‘maybe if I stop texting him back he’ll get the hint’. Sometimes, however, it evolves into a lifelong partnership. How does that happen?

I can’t tell you how to successfully transform your budding romance into a long-term partnership or how to keep yourself from falling in love with the person you’re casually seeing, but I will help you understand how your brain is essentially keeping you high on love and cuddles in the short-term until your prefrontal cortex has collected enough data to make a long-term decision.

First things first, to get it out of the way. Sex does not equal love – from a neurological perspective at least. Testosterone (an androgen) is the key player in the sex drive. Although its classically thought of as a male hormone, it plays important roles in females as well, specifically when it comes to libido. Generally speaking, higher levels of testosterone equals higher levels of sexual activity and has not been associated with ‘romantic love’ in humans (or other mammals, to my knowledge). And when humans use androgens to boost their sex drive, falling in love is not a side effect. All of this testosterone activity is playing out in limbic and paralimbic structures of the brain – areas that play important roles in more primal aspects of motivation, emotion, learning, and memory.

Now let’s look at falling in love. Someone catches your eye, you go for coffee, something seems to click and that person starts to be the focus of most of your thoughts, attention, and actions. This phase is typically relatively short-lived (12-18 months) and involves high levels of emotional dependence. In your brain, it looks a lot like addiction. Dopamine (which plays a key role in that rush you feel when you accomplish a goal) is a key factor in this early stage of love. It acts in the brain’s reward system, which plays a role in pleasurable feelings, focused attention, motivation and goal-oriented behaviours. This is the same system that gets hijacked by amphetamines and can help put into perspective some of the seemingly outlandish things people will do when they’re in love.

Of course, the brain is a beautifully complex thing, and the fact that these two systems are distinct, does not mean that they don’t interact. Studies in animals have suggested that doses of testosterone (to promote the libido) can lead to increased levels of dopamine (which can facilitate the feeling of falling in love) and vice versa. In fact, drug users have confirmed that amphetamines (which increases dopamine activity) increase sexual desire.

So both of these are (relatively) transient things. How do we explain my 90 year old grandparents who are still in a happy, committed relationship after 68 years of marriage? In animals, this is called pair-bonding (prairie voles are awesome at it), in humans, researchers refer to it as partner attachment, in lay English, its a long-term committed relationship. Regardless of the terminology, this is ‘a feeling of happy togetherness with someone whose life has become deeply entwined with yours’ (thank you to Elaine Hatfield and her 1982 book chapter ‘Passionate Love, Companionate Love, and Intimacy’ for that quote). There are a couple factors playing a role here. The first duo are oxytocin and vasopressin, these “cuddle hormones” or “love hormones” are involved in the neurological formation of attachments. These can be romantic attachments (as with partners) or familial attachments (as with parents and children). Oxytocin and vasopressin help “Netflix and Chill” turn into literally watching netflix and chilling (horrible metaphor, but I think you get where I’m going), they are what make you content when you’re spending time with the person you love for the long haul.

Even though neurotransmitters and hormones have gotten the majority of the glory so far, the other factor playing a role in long-term relationship maintenance is the general activity of the prefrontal cortex. This is the part of your brain that helps you evaluate options, weigh pros and cons, and make good decisions (it is also underdeveloped until your late teens/early 20s, which helps explain some of the poor decisions we made as teens). Prefrontal cortex involvement actually helps individuals in committed, long-term relationships down play any desire to date new individuals, thus helping with the maintenance of their existing relationship. It is also the part of your brain that helps you plan for your anniversary and know how upset your partner will be if you forget – but that wasn’t tested in the study.

A lot of the research backing this understanding was done in animal models, and while they’re cute and cuddly and can teach us a lot about how brains work, we can’t ask them for how they feel – we need humans for that. All of the connections outlined here have been confirmed in humans, but human love lives can be very complex and science likes to focus on one question at a time. So what do we really need to know? Sex, love, and long term relationships all involve different processes in the brain – they can interact and you can definitely enjoy multiple at a time, but each can occur completely independently of the other.



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