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Three

This Is Your Brain on Love

The way we’re wired, neurologically and hormonally, has a lot to do with how we think and feel—and when we think and feel it. But relationships exert their own powerful effects on the body and the mind. The first few months of attraction create a heady mix of neurotransmitters that no drug can adequately mimic. As a psychiatrist, I will say this: falling in love turns women into manic, obsessive, delusional junkies. At its most unromantic, falling in love is the neural mechanism of mate selection, evolved to ensure that we pine for, obsess over, and pursue the one person we believe will provide us with not only the fittest offspring but also the support to nurture that child through infancy. Falling in love with someone is an elaborate dance in the brain and body that motivates and focuses us on mating with this preferred partner. And in the early stages, the difference between falling in lust and falling in love can be difficult to distinguish. The progression from attraction to attachment is a physical process as much as it’s an emotional one. (Attachment, the phase that comes after attraction, has its own brain chemistry, which I’ll get to in the next chapter.)

Dopamine is the key chemical element of attraction, underlying the experiences of paying attention, sensing pleasure, and seeking reward. Dopamine tells us two things: “Notice this important thing” (called salience) and “This feels good; do it again.” The reward circuitry runs on dopamine, the molecular cornerstone of addiction. Drugs that enhance dopamine levels, like cocaine and speed, are more likely to be addictive than other drugs; many researchers believe a drug can’t be addictive without at least secondarily increasing dopamine transmission.

When you fall in love, dopamine makes you crave and need your newfound crush. The object of your affection is specific, partly because dopamine has tagged him or her as salient. Experiments with prairie voles, typically monogamous, showed that higher levels of dopamine were responsible for preferring a particular partner, and blocking dopamine decreased that partner preference. In anthropologist Helen Fisher’s brain scans of people who fell deeply in love, their dopaminergic reward systems were kicked into high gear, reminiscent of brain scans of people high on cocaine. Increased blood flow was seen in the caudate nucleus, an area fed by dopamine neurons. Sometimes referred to as the “motor of the mind,” the caudate directs your body to approach the target, motivating you to go after the reward. Dopamine ensures that this is a pleasurable process, making the behavior reinforcing, meaning you’ll gladly do it repeatedly.

Addiction is characterized by three things: sensitization, tolerance, and withdrawal. Over time, smaller triggers will induce a craving, more substance is required to induce pleasure, and going on the wagon feels terrible. You see the same increase in wanting, in appetite and desire, whether for a drug or for a crush. And if the object of your desires breaks it off, your brain chemicals nosedive into abrupt withdrawal. Expect a bad crash. Crying, sleeping, and bingeing on food and alcohol are common in my jilted patients. If you reunite, some portion of the feel-good chemistry reappears, convincing you that you were meant to be together. But don’t be fooled by your pharmacological homecoming party—junkies feel good when they relapse, too, at first. It doesn’t necessarily mean he’s the one, but it should help to explain the particular pleasure of makeup sex. You fight; you feel ultraterrible because you’re in withdrawal from your lover and a whole lot better, and higher, once you are reunited.

The dopamine reward circuitry underlies not just pleasure but the anticipation of more pleasure and the motivation to get it. This may be the biological logic underlying the age-old advice to play hard to get and the dating advice book The Rules. Studies show that getting the reward too early in the game reduces the intensity and the duration of the brain’s dopamine activity. A delay in the win gives the most pleasure, potentially benefiting both of you.

But dopamine alone is not responsible for that blissful feeling of finding Mr. Right. Falling in love stimulates the release of norepinephrine, a chemical cousin of adrenaline, which keeps you excited and energized, with sweaty palms and a rapid heartbeat. Norepinephrine revs up all five senses, the better to heighten awareness and remember every detail of your love object and his or her effect on you. Your brain and body are on high alert, primed for action and reaction. Sleep is optional. So is food, for that matter.

Norepinephrine also contributes to the release of estrogen, which stimulates courting behavior. Increased levels of these two chemicals are seen in laboratory animals striking a sexually inviting pose known as lordosis. Arching the back and sticking the butt up in the air makes it easier for rear-entry penetration. There may be a human equivalent of lordosis, seen in the posture created by high heels, or, more obviously, in Miley Cyrus’s twerking.

Add to the cocainelike mix of dopamine and norepinephrine a healthy shot of endorphins, our naturally circulating opiates, nature’s painkillers and stress relievers. So falling in love is pharmacologically a bit like a speedball, the combination of cocaine and heroin. But there’s more, because experiencing intense infatuation, and especially love at first sight, is like taking a psychedelic drug, too. Phenylethylamine (PEA), sometimes dubbed the “molecule of attraction,” floods the brain when the initial magnetism occurs. PEA is responsible for some of the dreaminess and giddiness when first falling in love. It may underlie love at first sight, and it’s likely present in your brain during that all-important first kiss. Phenylethylamines naturally occur in your brain, but they’re also found in a group of drugs that includes ecstasy (MDMA) and some hallucinogens. PEA also kills appetite and can work as a short-term antidepressant. It is present in good chocolates, and it may also spike during orgasm, causing that trippy, out-of-body feeling that some women are lucky enough to experience.

With all of these stimulating chemicals bathing the brain, it’s no wonder many women who fall in love find it easier to lose weight and exercise and harder to fall asleep at night. One thing I’ve noticed repeatedly: when my patients fall in love, they can more easily go off their antidepressants and quit me. I can’t devise a medication cocktail that can compete with what your brain will concoct in the early glow of a relationship. In fact, there are those who so enjoy the brain chemistry of the infatuation phase that they become serial attraction junkies. They fall in love, stay high for three to six months, and when the magic fades they move on.

There are other chemical players on the team during the initial attraction phase. The levels of the sex hormones testosterone and estrogen are higher when falling in love. They enhance sexual desire and receptivity, respectively. Estrogen and progesterone both enhance the love/trust circuits, so as long as you’re not in PMS land, you may be more open to loving and nurturing behavior. But in terms of being horny, it’s all about testosterone. Men and women with higher levels of circulating testosterone engage in more frequent sex and have more orgasms. Men who inject testosterone (for performance enhancement on the athletic field or on Wall Street) experience more sexual thoughts and more morning erections and have more sex. But they don’t necessarily fall in love.

When women fall in love, increased dopamine levels can enhance testosterone levels. Also, inhaling male pheromones can trigger testosterone release in a receptive woman. Just thinking about your new guy can raise your levels. Interestingly, men who are falling in love have slightly lower levels of testosterone than usual, perhaps so they don’t scare off their new mate with how horny they typically are the rest of the time! So while we fall in love, women’s testosterone levels bump while men’s dip, which may give us a chemically unifying feeling that we’re in this experience together, and we are evenly matched in terms of libido.

How all of this works when gay men or lesbians form lasting unions is hard to fully address, mostly because there’s a lot less research in this area. Obviously, same-sex couples can and do create healthy, loving unions and families. Their brains give them the same pleasurable, heady mixes when they become infatuated, fall in love, and form binding attachments, proof that what brings us together is about more than just procreating.

Hugs, Not Drugs

Oxytocin makes you feel great. Do you know that ultrarelaxed feeling you get when you hold your baby? How about the bliss after you’ve just had orgasmic sex and are being held closely? That’s oxytocin, the hormone of bonding and of trust. A twenty-second hug will trigger oxytocin release, as will exchanges of friendly signals, like being smiled at and returning the grin. Think of oxy as superglue for your relationship. It cements a nursing mother and her child, and it bonds lovers from the first time their eyes lock across a crowded room. Holding hands, kissing, and sex will all get your oxy levels zooming. Smiling babies and hugs with boyfriends activate not only oxytocin release but also dopamine-associated brain reward circuits, encouraging us to keep doing it. In that way, you could say that oxytocin makes you crave even more physical contact. Oxytocin helps to protect us against stress and promote relaxation. There are even some studies showing it can help to speed healing. So hugging, cuddling, and orgasmic sex are good for not just your heart and soul but your body as well.

Women have more oxytocin receptors in their brains, and oxytocin works better in an environment rich with estrogen. So you may be more likely to connect and fall in love during the first half of your cycle, before estrogen levels drop. Oxytocin, in both men and women, creates feelings of trust, connection, and contentment around the preferred partner. Oxytocin reduces heart rate and blood pressure, enabling social bonding and trusting behaviors. A sense of calm and security quiets the typical fear of strangers, allowing more generosity. In experiments, people given oxytocin are more willing to trust a stranger or give them money. That may be the reason why people who are touched while spoken to are more likely to honor a request or keep a promise. It also may be why falling in love can be dangerous for some. I had a patient who lent way too much money to a new boyfriend who later disappeared.

Infatuation overrides rational thought. At higher levels of oxytocin, you may become forgetful, and your ability to think clearly may be diminished. Falling in love squelches anxiety and skepticism. Oxy, in particular, seems to be crucial for inhibiting fear and anxiety, allowing bonding and sex to occur. When people fall in love, their fear circuitry gets turned way down, so the critical thinking system (anterior cingulate cortex) and the fear center (amygdala) are less active. The brain’s Miracle-Gro fertilizer, a nerve growth factor called brain-derived neurotrophic factor (BDNF), which helps to foster new connections between nerve cells, is elevated in people who’ve fallen in love, triggering a massive neuronal reorganization. (Remember BDNF, because you’re going to be learning about it again. Neuroplasticity is involved in pregnancy, perimenopause, and exercise, and it’s important.) Tons of brain cells have to be “obliterated and replaced with new ones. This is one reason falling in love feels . . . like a loss of identity.” Is all of this dangerous? Probably not, but it’s good to keep your wits about you when falling in love. You’re not in your typically critical “right mind.” You’re not even yourself!

You’re My Obsession

Ask my husband about how we met and he’ll say he’s never been pursued by anyone more aggressively in his life. Ask me, and I’ll tell you about love at first sight. I remember every moment of that party where I set my eyes on him. I had to lock myself in the bathroom to calm down my breathing and pounding heartbeat (norepinephrine in action). In the days that followed, I would check countless times to see if he’d contacted me. All day long, I could think of nothing but him, Him, HIM.

It’s normal, it’s nature’s way, and it’s likely that lower than normal serotonin levels were underlying my obsessive thoughts and activities. When serotonin levels are high, there is a sense of satiety; you want for nothing. When levels are lower, you become obsessive and angsty. Blood serotonin levels in those newly in love resemble levels in people with OCD. They’re abnormally low for both, about 40 percent of the normal controls.

Dopamine and serotonin tend to act like they’re on opposite sides of a seesaw. When one is up, the other is often down. Infatuation and initial attraction are characterized by higher dopamine and lower serotonin levels. Higher serotonergic states make it harder to climax, as anyone on sertraline can tell you. So this low serotonergic state helps explain not only why it’s easier for you to climax with your new lover but also your tremendous feelings of angsty need and obsessive ruminations about your newfound love.

One thing I’d like to stress: women on SSRIs likely won’t experience some of the chemical cocktail of attraction and infatuation. SSRIs create artificially high serotonin levels, decreasing impulsive and compulsive behavior. You have more behavioral control, and you don’t obsess as much about anything, even if you just fell in love, which you may not even do on an SSRI. SSRIs interfere with mating in a few crucial ways. As serotonin and dopamine often balance each other out, if serotonin is too high, dopamine levels will be low. Emotional blunting and apathy result. It’s hard to go out and chase down a guy when your “Go get ’em, tiger!” neurochemical is lacking. Also, there’s less chance of your getting obsessive and fixated on one preferred partner when you are taking a medicine meant to treat OCD. If high dopamine and low serotonin drive the rewarding and obsessive nature of falling in love, being on an SSRI, with its resultant low dopamine and high serotonin levels, won’t drive the behavior. Female rats treated chronically with SSRIs reduce the amount of time they spend near males. Sex researchers are currently conducting studies showing that women on SSRIs rate men as less attractive and spend less time poring over images of their faces than women who aren’t on SSRIs, being “less likely to find those of their chosen sex physically attractive or desirable as a potential romantic or sexual partner.” Just as I recommend my patients get off oral contraceptives when mate shopping, there are reasons to slowly taper off antidepressants as well. If being on SSRIs means you already feel satiated and don’t even look twice at a guy, it’s going to be hard to move forward from attraction and infatuation to attachment.

Falling in love and choosing a mate rely on sexual attraction and sexual energy. If libido is lowered and sexual response is muted by an SSRI, it seems obvious that this will have a negative impact on the entire process. The neural systems associated with attachment and pair bonding also rely on orgasm and its resulting surge of oxytocin. Because SSRIs make orgasm much more difficult, they jeopardize this major trigger. One way that a woman can judge a potential partner is by how much time and attention he’s putting toward her pleasure. “Scientists think the fickle female orgasm may have evolved to help women distinguish Mr. Right from Mr. Wrong.” A man who can pay extra time and attention to a woman’s needs may also be a better father and more willing to share what he has (a dad and not a cad). Perhaps unconsciously, a woman may use her ability to climax with a certain partner to help her decide whether he is the one for her and her future children, or not so much. If it’s nearly impossible for her to be aroused all the way to orgasm because of her SSRI, then she can’t make use of this measuring device.

Lust

From an evolutionary perspective, you could say lust is practice for love. Learning to flirt to attract a mate, and practicing what to do when you find a potential partner, need to be finessed repeatedly over time. The chemistry of lust and attraction are similar, but not the same. Testosterone makes us horny, dopamine keeps us moving forward, and oxytocin frees us up from the fear of strangers so we can shed our clothes and get close. But with lust, a biological drive for sexual gratification, it’s more about testosterone and less about oxytocin.

Estrogen may make us more receptive to sex, taking the brakes off and helping us to be uninhibited, but testosterone is the gas pedal. Even flirting seems to have some basis in testosterone. While romantic love is reserved for one preferred partner, the target of lust isn’t the perfect man, but rather “almost any semi-appropriate partner”; it’s not Mr. Right so much as Mr. Right Now. Also, the neural mechanism of attraction won’t allow you to fall in love with two different people at once, but you can lust after more than one person at a time. Another key difference is that the fires of lust are quickly doused once the sex is over; with attraction, repeated sex just adds to the buildup of good feelings.

In women, testosterone is made in the adrenal glands and ovaries, spurring our competitive drive, our assertiveness, and our lust. In adolescence, a girl’s level of testosterone rises five times above normal, but it is in the context of her estrogen increasing ten to twenty times above normal, so it’s balanced out to a large extent. Adolescent boys have a twenty-five-fold increase in their testosterone, unabated by other mitigating hormonal factors, which means they have much higher sex drives than the girls. Also, in boys these levels are static, whereas girls have cyclical variation. Boys’ behavior ends up being much more consistent, basically a constant stream of horny. Boys have more frequent sexual thoughts and more masturbation, which is not to say girls aren’t doing it, too, just not as much. Interestingly, surging testosterone levels in an adolescent girl can signal the time of first intercourse.

Women have different standards for hookups versus getting hitched. In the past few years, numerous articles have been written about how today’s women, whether in college or out in the world soon after, are so focused on getting their careers off the ground that they prefer more casual sex over complicated long-term relationships. They’d rather get their gratification on their own terms and not muck it up with messy feelings like love. Since “women’s lib” and oral contraceptives have become commonplace, women have had growing freedom in this arena. Having sex has become uncoupled from committed relationships and the responsibilities of motherhood. This is a relatively new phenomenon, and I totally get it. But one warning about one-night stands, just so you aren’t fooling yourself. Lust and sex can trigger feelings of attraction and even love. Rising testosterone levels can enhance dopamine and norepinephrine transmission and lower serotonin, matching the brain chemistry of someone who’s falling in love. And sex can definitely trigger attachment and bonding, due to oxytocin. Testosterone can trigger oxytocin release, and an orgasm will definitely trigger oxytocin release. If you orgasm or cuddle after sex, the bonding hormones may sneak up on you, though you intended your sex to be casual. Thanks to oxytocin, you may find yourself with loving, attached feelings for your Mr. Right Now.

There is a strong desire in women to be held and cuddled. Many of us will use sex as a means to an end, hoping to have some afterglow and snuggling, willing to trade sex for that experience. Men, too, are eager to be held. A common complaint among men in sex therapy is that they don’t receive enough nonsexual touching. But getting naked and cuddling is going to trigger oxytocin, the bonding hormone. So you may find that it’s hard for you to keep your “friend with benefits” in that same category for long.

The Chemistry of Sex

Your brain on sex is like a series of loops. Hormones may trigger behaviors, but just as often, behaviors trigger hormones. Sexual activity stimulates testosterone release, which further revs up desire and triggers dopamine release. This dopamine-laden euphoria and arousal further trigger testosterone release. Sensitivity to touch is enhanced by dopamine and particularly by oxytocin. The more skin-to-skin contact, cuddling, kissing, eye gazing, and nipple stimulation, the more oxytocin gets released, which triggers testosterone, then dopamine.

Oxytocin and endorphins not only stoke arousal and pleasure but also help produce feelings of closeness and relaxation. As a woman becomes aroused by stimulation of her nipples, oxytocin gets released, just as it is when suckling a newborn. Further attention to her vagina, clitoris, or cervix creates more oxytocin and estrogen release, resulting in an acute drive to become penetrated, and an expansion of the vaginal muscles in case that’s what will happen. Estrogen is involved in every phase of sex, making women more sexually receptive and lubricated and triggering oxytocin release. As sex progresses, oxy increases, culminating in an orgasmic burst. Estrogen and testosterone put the brain on high alert, so that dopamine and norepinephrine, our two “stand up and take notice” chemical friends, can get involved. Dopamine, of course, makes us pay attention to a potentially rewarding stimulus like sex. It gives us pleasure, enhances sensory input, and triggers the reward circuitry that motivates us to keep going, driving us toward orgasm.

You have two competing systems in your body: sympathetic and parasympathetic. The sympathetic is the fight-or-flight system, while the parasympathetic is the rest-and-digest system. Norepinephrine jump-starts the sympathetic nervous system, increasing heart rate, raising blood pressure, and causing heavy breathing. Balancing this out, the parasympathetic system also gets in on the act, directing blood flow to the genitals. Sex is a delicate balance of sympathetic and parasympathetic stimulation, toggling back and forth. Too much adrenaline-like arousal early on, and plateau or orgasm may be difficult, if not impossible, as is seen with stimulants like cocaine and speed. (There are those people, though, who need a short burst of adrenaline in order to get over the finish line.)

For the finale, endorphins take center stage, helping us to feel great and make sex something we’ll want to do repeatedly. Endorphins also raise our pain threshold. Response to pain is just half of normal during the peak of sexual arousal. Does that help explain nipple clamps? Not only do they hurt less when you’re extremely aroused and high on your brain’s own heroin, but there is some overlap in the brain when it comes to sexual pleasure and pain, as their circuitry is closely linked. If you’re also curious about anal sex or toe sucking, anal sensations travel some of the same routes as genital sensations, and the area in the brain that maps out physical sensations from the genitals is right next to the one for the toes. Stimulate either area enough and you get some carryover into the genital sensation part of the brain. And breast and genital neural circuitry overlap as well, which may explain why some women can orgasm from nipple stimulation alone. Isn’t the brain marvelous? Also, there is mounting evidence that sexual pleasure triggers the endocannabinoid system as well, your body’s internal cannabis molecules.

The Chemistry of Orgasm

Orgasms are good for you. They reduce mortality, are good for your heart and cardiovascular system, help to prevent endometriosis, and when the time is right, they help you to conceive and carry a pregnancy to term.

The beginning of sexual pleasure is dopamine mediated, while the second act is primarily endorphins, which crescendo with orgasm. Oxytocin and dopamine are the big players leading up to orgasm, but the climax itself owes its mind-bending effects to the triple threat of oxy, endorphins, and PEA, the hallucinogen-like brain chemical, which just might make you feel like you really were “way out there” when you climaxed. Trippy, out-of-body experiences, or laughing, crying, and switching between the two, are all possible and normal during an orgasm.

Oxytocin keeps you feeling connected to your lover. It also permits relaxation, helping you feel calm, secure, and trusting enough to climax. Peaking at orgasm, oxytocin causes uterine contractions, which help to “suck up” semen into the cervix. It also can engender tremendous feelings of openness, trust, and bonding. The oxy afterglow lasts between one and five minutes postorgasm in women.

After orgasm, serotonin peaks, creating one happy, relaxed, sexually satisfied, and satiated sensation. In some women after orgasm, a negative feedback loop is triggered, with prolactin secretion making them sleepy, dopey, and, often, significantly less horny. Still other women respond to the heightened pleasure with one thought in mind: I wanna go again. Sometimes all that dopamine, norepinephrine, and testosterone continue to trigger sexual desire. Also, the oxytocin creates more touch sensitivity and a desire for more skin-to-skin cuddling, which can trigger another round of testosterone surge.

Brain Blood Flow in Orgasm—All the Wonky Details

Barry Komisaruk’s lab at Rutgers University in northern New Jersey is the world’s largest orgasm research laboratory. Here, men and women are slid into an MRI chamber, where they must lie completely still, their heads held immobile in a mesh cage. Their brain blood flow is then measured while they give themselves, or receive, orgasms. Over the years, this lab has studied just what it takes to climax, including looking at women who can orgasm through fantasy alone and others who’ve had their spinal cords severed, to see if they can climax. (They can, as long as their vagus nerve, which innervates the genitalia, is intact.)

The lab’s more recent studies are delineating the difference between self-stimulation and partner stimulation. Most of us would be quick to agree that these two orgasms are qualitatively different, especially in the emotional realm. The question is: are they physiologically different? Early results suggest they are.

During orgasm, fresh oxygen- and nutrient-rich blood floods the brain. Leading up to orgasm, a series of brain blood flow changes occur. First is activation of the somatosensory cortex, the part of the brain that maps out bodily sensations. Next seen is decreased blood flow to the frontal cortex. You want less frontal flow because you need your foot off the brakes to move a car forward. Frontal inhibition will put the kibosh on the entire sequence. Soon after, the secondary somatosensory cortex, which adds the emotional piece to your physical sensations, is activated. Then increased blood flow is seen in the amygdala, your emotional center, and then in the part of the hypothalamus that is responsible for the release of oxytocin.

The last piece of the puzzle is the dopamine circuitry that underlies reward seeking, pleasure, and euphoria. The final push into orgasmic bliss is the job of this brain area. Dopamine not only helps you pay attention, focus, and keep your eyes on the prize, but it also marks an event as salient. So don’t be surprised if the guy you were only moderately into suddenly becomes more important in your eyes after he’s given you the big O. Dopamine surges also decrease sensory thresholds for more sensation, priming the brain for more pleasure. Multiple orgasms, anyone? (For more on sexual pleasure, please enjoy the sex chapter.)