Do you have a friend who is always getting into relationships? It seems like she is always meeting someone new, and by the time you have learned the name of her latest significant other she is introducing you to somebody else a few weeks later. Though you might find this strange and a bit annoying, your friend, like many others, may very well be addicted to love.

The mesolimbic pathway is a neural circuit that is referred to as the reward pathway. This pathway contains a few important brain structures, including the ventral tegmental area, the nucleus accumbens, and the prefrontal cortex (Alcaro et al., 2007). Dopamine is heavily implicated in this reward pathway.  Dopamine is a neurotransmitter with many roles, including regulation of emotional responses, pleasure, and the ability to see and take action toward rewards (Ayano, 2016).    

When we experience reward, our mesolimbic dopaminergic pathways are activated. Natural rewards, like food and sex, and synthetic rewards like drugs increase the amount of dopamine that gets deposited in the mesolimbic pathway. Romantic love can also increase dopamine levels in the mesolimbic pathway.

Romantic love is defined as a state of intense longing for union with another person (reviewed in Zou et al., 2016). Romantic love undergoes multiple stages. The first stage of romantic love is falling in love. This phase is characterized by excitation and stress. After roughly six months, things begin to change, and the relationship enters a phase of calmness, balance, and safety (reviewed in Zou et al., 2016).

In the earliest phase of romantic love, we feel intense emotion and a sense of euphoria. We focus intensely on our loved ones, obsessing over them, and we may even develop an emotional dependence on our union with this person (Zou et al., 2016). When we hear the words euphoria, dependence, and obsession, we may think of addiction. In fact, many researchers actually consider romantic love to be a behavioral addiction (reviewed in Zou et al., 2016).

The notion that romantic love impacts the brain in a similar way as addiction has some important implications for how we study drug addiction. As previously mentioned, romantic love undergoes two stages. Some researchers examine brain changes that occur during the two phases of love to study the development of drug addiction (Zou et al., 2016).  In the early phase of drug use, drug initiation is marked by fleeting changes in neural functioning. These changes can last for hours, even weeks during periods of abstinence. In the second phase of addiction, drug use becomes compulsive, and changes to the brain become more stable. These stable changes can become permanent and maintain the addiction (reviewed in Zou et al., 2016).  Researchers have sought to gain a better understanding of the neural basis of addiction by studying the brains of people in love.

To study differences in the neural activity of people in love, researchers have used functional magnetic resonance imaging (fMRI) to compare the brains of individuals who are in love to the brains of people who are single and have never fallen in love before. fMRI studies allow researchers to compare the regional homogeneity and functional connectivity of the brains. Regional homogeneity refers to the connection between different brain nodes, whereas functional connectivity refers to how different regions of the brain are related to each other (Xiang & Zuo, 2015).

In people who were in the “in love” group, there was significantly more activity in the dorsal anterior cingulate cortex compared to the brains of single people who were not in love. The amount of regional homogeneity in this part of the brain was positively correlated with the amount of time people were in love (Song et al., 2015). The dorsal anterior cingulate cortex plays a role in motor functioning and cognition. It also has been implicated in reward based decision making (Bush et al., 2001). In the “single” group, activity in the left dorsal anterior cingulate cortex was negatively correlated with the length of time since a break up. Activity in the brain networks that control emotion and social cognition was significantly greater for people in the in love group than in the single group. The results from this study indicate that being in love actually causes distinct changes in brain activity and structure (Song et al., 2015).

While you might get annoyed with your friend who always seems to be in love, we can actually learn a great deal about addiction and our dopaminergic reward pathway by studying her brain and the brains of other love birds. Imaging studies indicate that romantic love and drug addiction lead to some similar neural changes and that both are implicated in the dopamine reward system. These studies also alert us to the important neural differences between romantic love and drug addiction and may help inform the ways we treat addiction (Song et al., 2015).

References

Adinoff B. Neurobiologic processes in drug reward and addiction. Harv Rev Psychiatry. 2004;12(6):305–320. doi:10.1080/10673220490910844

Alcaro A, Huber R, Panksepp J. Behavioral functions of the mesolimbic dopaminergic system: an affective neuroethological perspective. Brain Res Rev. 2007;56(2):283–321. doi:10.1016/j.brainresrev.2007.07.014

Bush G, Vogt BA, Holmes J, et al. Dorsal anterior cingulate cortex: a role in reward-based decision making. Proc Natl Acad Sci U S A. 2001;99(1):523–528. doi:10.1073/pnas.012470999

Jiang L, Zuo XN. Regional Homogeneity: A Multimodal, Multiscale Neuroimaging Marker of the Human Connectome. Neuroscientist. 2015;22(5):486–505. doi:10.1177/1073858415595004

Song H, Zou Z, Kou J, et al. Love-related changes in the brain: a resting-state functional magnetic resonance imaging study. Front Hum Neurosci. 2015;9:71. Published 2015 Feb 13. doi:10.3389/fnhum.2015.00071

Zou Z, Song H, Zhang Y, Zhang X. Romantic Love vs. Drug Addiction May Inspire a New Treatment for Addiction. Front Psychol. 2016;7:1436. Published 2016 Sep 22. doi:10.3389/fpsyg.2016.01436