Different theories have pointed out for years that it is not possible for the intensity of love to last over time and that love, and over the years, is transformed into a deep friendship. However, in 2011, neuroscientist Lucy L. Brown of the Albert Einstein College of Medicine, together with Helen Fisher, suggested that there might be mechanisms by which love could be sustained over time in a relationship and described what happens in the relationship. brains of couples with long-term relationships. To find out, they picked ten men and seven women married for an average of 20 years and underwent MRI scans, showing them pictures of their partners, close friends, close relatives and distant relatives.

 The results showed that when they saw the image of their partner, their brain behaved in a similar way to that of people who have just fallen in love, by activating the regions that make dopamine, the hormone responsible for euphoria, common in the beginning of relationships and a neurotransmitter that regulates the reward system, responsible for us to respond to stimuli that cause pleasure or displeasure. Therefore, magnetic resonance imaging has revealed that the same areas are activated in the brains of some couples who have been together for decades as in new lovers. This together with the levels of oxytocin, the “hug hormone” and together with a dose of overexertion, love should have the ingredients to be long-lasting. common in the beginning of relationships and neurotransmitter that regulates the reward system, responsible for us to respond to stimuli that cause pleasure or displeasure. Therefore, magnetic resonance imaging has revealed that the same areas in the brains of some couples who have been together for decades are activated as in new lovers. 

 This together with the levels of oxytocin, the “hug hormone” and together with a dose of overexertion, love should have the ingredients to be long-lasting. common in the beginning of relationships and neurotransmitter that regulates the reward system, responsible for us to respond to stimuli that cause pleasure or displeasure. Therefore, magnetic resonance imaging has revealed that the same areas are activated in the brains of some couples who have been together for decades as in new lovers. This together with the levels of oxytocin, the “hug hormone” and together with a dose of overexertion, love should have the ingredients to be long-lasting.

 However, the love cycle is not constant and means that while romantic love begins with high doses of passion and increasing intimacy, it gradually transforms into partner love where passion decreases, intimacy is maintained and commitment increases. Kisses are part of the love passion, which is the desire to join the other. This stage lasts from 5 to 12 months and, later on, there is a feeling of habituation in which the feeling of exaltation is replaced by another of calm and security, and the attachment is consolidated. With the passage of time, people get used to being with the other, to not missing it, and the same passion is no longer lived because there is greater security regarding the relationship, even so, passion does not disappear definitively, since it can be revived, incorporating new elements into the relationship.

 Many couples do not accept the change from "romantic love" to "partner love" and wrongly interpret it as the end of love. However, it is in this change, when the extreme passions of passionate love are transformed into the true keys to a lasting relationship, these being communication, tenderness, affection and satisfaction.