Dr. Helen Fisher categorizes love into three types based on hormonal influences and brain mechanisms. Lust is attributed to high levels of androgens and estrogens, while romantic love is linked to increased dopamine and norepinephrine, along with decreased serotonin. Attachment is connected to oxytocin and vasopressin, and these three systems are interrelated. For instance, testosterone can stimulate romantic feelings, and orgasms can boost attachment hormones.

Fisher advises caution in sexual relationships, suggesting that one should avoid intimacy with individuals they do not wish to develop strong feelings for. This interconnectedness of the hormonal systems implies that engaging in physical relations can inadvertently lead to deeper emotional bonds.