Daily experience of love seems to indicate that this feeling profoundly looks like addiction to drugs of abuse. Here, I would like to evaluate and compare both phenomenon.
In an evolutionary view, love is critical for reproduction and thus for the survival of species. It is now well known that oxitocyn is involved in numerous sociosexual behaviours in mammals like sexual behaviour (Witt and Insel, 1991) or the formation of pair bond in monogamous species (Young et al., 2001). It has been shown that monogamous rodents express more oxitocyn receptors (OTR) in the Nucleus Accubens (NAcc) than non-monogamous rodents (Insel and Shapiro, 1992). We can, then, imagine that oxitocyn could activate the mesocorticolimbic ‘reward pathway’ by modulating the dopamine release in the NAcc through OTR. Behaviours that activate the dopaminergic pathway are called ‘natural rewards’ (Comings and Blum, 2000) and love, which also involves oxitocyn, is a behaviour that activate this pathway. So, love is a behaviour which act, partly, through the dopaminergic rewarding pathway.
The mesocorticolimbic pathway is also a center in the establishment of addiction. An original way to evaluate the addictive aspect of love is to study the rupture between two people. Indeed, the end of a romance often leads to unpleasent feelings for, at least, one of both protagonists. These unpleasent feelings are most commonly sadness, dysphoria, anxiety, panic attacks, sleep disturbance and depression. We can observe that most, if not all, of these feelings overlap symptoms of withdrawal for drug that increase mesocorticolimbic dopamine (Rabinak and Nirenberg, 2010).
Furthermore, the drug administration environment is well known to play a key role in the establishment of addiction (Wise, 2004; Everitt and Robbins, 2005). It is not rare to encounter well-intentioned people who say “leaving this city will help you to forget her”. This advise is based on the same mechanisms than those involved in the relation between addiction and contextual cues. However, the learned association between the drug and its administration environment is very specific. This form of learning involves the encoding of highly detailed information about drug effect and complex sets of cues in the drug administration environment (Koya et al., 2009). This is not found with love. Indeed, love feelings retrieval doesn’t require a highly detailed environment. Thus, the simple odour of her perfume, somebody dressed like her, a similar voice, her favourite song, etc... each individual cue can generate the recall of complex memories linked to her lover.
Finally, addiction has been linked to a low concentration of dopamine D2 receptors in the NAcc (Dalley et al., 2007). We saw that love feelings share neuronal substrates that also support addictive behaviour. But any study (to my knowledge) reports such a decrease in D2 receptor expression in lovers striatum. However, it is obvious that people who are in love with somebody shouldn’t express a reduced expression of D2 receptor. Otherwise, love could be seen as a psychiatric disorder.
In conclusion, we saw that love shares lot of common aspects with addiction and it is not impossible that they have common neuronal substrates. We also saw that love has some specific aspects which differ with addiction. In fact, if love is a drug, we can say that it is the most strong and addictive substance we have never seen.
But, love is too important to be studied by neurosciences as a simple mechanical behaviour. So forget everything !
Aknowledgements
I would like to thanks PBS and CSCP who allowed me to use their Pumed acces. Without them, this work wouldn’t exist.
References:
Comings and Blum, Prog Brain Res, 2000
Dalley et al., Science, 2007
Everitt and Robbins, Nat Neurosci, 2005
Insel and Shapiro, Proc Natl Acad Sci USA, 1992
Koya et al., Nat Neurosci, 2009
Rabinak and Nirenberg, Arch Neurol, 2010
Witt and Insel, Endocrinology, 1991
Wise, Nat Review, 2004
Young et al., Horm and Behav, 2001
In an evolutionary view, love is critical for reproduction and thus for the survival of species. It is now well known that oxitocyn is involved in numerous sociosexual behaviours in mammals like sexual behaviour (Witt and Insel, 1991) or the formation of pair bond in monogamous species (Young et al., 2001). It has been shown that monogamous rodents express more oxitocyn receptors (OTR) in the Nucleus Accubens (NAcc) than non-monogamous rodents (Insel and Shapiro, 1992). We can, then, imagine that oxitocyn could activate the mesocorticolimbic ‘reward pathway’ by modulating the dopamine release in the NAcc through OTR. Behaviours that activate the dopaminergic pathway are called ‘natural rewards’ (Comings and Blum, 2000) and love, which also involves oxitocyn, is a behaviour that activate this pathway. So, love is a behaviour which act, partly, through the dopaminergic rewarding pathway.
The mesocorticolimbic pathway is also a center in the establishment of addiction. An original way to evaluate the addictive aspect of love is to study the rupture between two people. Indeed, the end of a romance often leads to unpleasent feelings for, at least, one of both protagonists. These unpleasent feelings are most commonly sadness, dysphoria, anxiety, panic attacks, sleep disturbance and depression. We can observe that most, if not all, of these feelings overlap symptoms of withdrawal for drug that increase mesocorticolimbic dopamine (Rabinak and Nirenberg, 2010).
Furthermore, the drug administration environment is well known to play a key role in the establishment of addiction (Wise, 2004; Everitt and Robbins, 2005). It is not rare to encounter well-intentioned people who say “leaving this city will help you to forget her”. This advise is based on the same mechanisms than those involved in the relation between addiction and contextual cues. However, the learned association between the drug and its administration environment is very specific. This form of learning involves the encoding of highly detailed information about drug effect and complex sets of cues in the drug administration environment (Koya et al., 2009). This is not found with love. Indeed, love feelings retrieval doesn’t require a highly detailed environment. Thus, the simple odour of her perfume, somebody dressed like her, a similar voice, her favourite song, etc... each individual cue can generate the recall of complex memories linked to her lover.
Finally, addiction has been linked to a low concentration of dopamine D2 receptors in the NAcc (Dalley et al., 2007). We saw that love feelings share neuronal substrates that also support addictive behaviour. But any study (to my knowledge) reports such a decrease in D2 receptor expression in lovers striatum. However, it is obvious that people who are in love with somebody shouldn’t express a reduced expression of D2 receptor. Otherwise, love could be seen as a psychiatric disorder.
In conclusion, we saw that love shares lot of common aspects with addiction and it is not impossible that they have common neuronal substrates. We also saw that love has some specific aspects which differ with addiction. In fact, if love is a drug, we can say that it is the most strong and addictive substance we have never seen.
But, love is too important to be studied by neurosciences as a simple mechanical behaviour. So forget everything !
Aknowledgements
I would like to thanks PBS and CSCP who allowed me to use their Pumed acces. Without them, this work wouldn’t exist.
References:
Comings and Blum, Prog Brain Res, 2000
Dalley et al., Science, 2007
Everitt and Robbins, Nat Neurosci, 2005
Insel and Shapiro, Proc Natl Acad Sci USA, 1992
Koya et al., Nat Neurosci, 2009
Rabinak and Nirenberg, Arch Neurol, 2010
Witt and Insel, Endocrinology, 1991
Wise, Nat Review, 2004
Young et al., Horm and Behav, 2001
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