I’ve often heard men say, “I love looking at porn. Besides it doesn’t hurt anything. It’s only fantasy. What’s the problem?”

Now, you may not have a moral problem with porn, but many are starting to have a medical problem with it. The more we study the impact of porn on the male brain, the more men are starting to think twice about porn being a harmless pastime.

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1. Porn gives men a new standard of beauty.

In 2002, the Journal of Sex and Marital Therapy, published research showing that when men are shown pictures of centerfold models from Playboy and Penthouse, this significantly lowered their judgments about the attractiveness of “average” people.

In our hyper-sexualized media culture, is this something that really needs to be reinforced? Should we train our brains to rate women by the size, shape, and harmony of their body parts? Do we want our standard of beauty to be shaped by a fictional standard or by the woman we are actually in love with?

Related: 5 Ways Sex Gets Better After Giving Up Porn

2. Male brains don’t just view porn. They enter into it.

The journal NeuroImage published a study in 2008 demonstrating that as men are sexually aroused by porn films, something called “mirror neurons” in the brain also fire.

What is a mirror neuron? Have you ever seen someone get hit in the face with a ball or some other blunt object, and then your own body recoils? This is because of mirror neurons: you instantly react as if you were the one hit.

When it comes to porn, the brain naturally imagines the viewer in the pornographic scene. When a man is turned on by porn his body is not merely responding to the naked woman. His brain is picturing himself as the main character, heightening the arousal. You see, porn isn’t merely arousing to men because the women in it are attractive, but because it makes the man feel sexy.

This trains men not to get their sense of personal validation from real life relationships but from pixels on a screen.

3. The more porn men watch, the more their brains look like an addict’s brain.

In 2014 scientists at Cambridge discovered that the brains of habitual porn users show great similarity to the brains of alcoholics. When a self-confessed porn addict is hooked up to an MRI machine and then is shown a pornographic image, a brain structure called the ventral striatum “lights up” in the same way it lights up for an alcoholic who sees a picture of an drink.

You might be thinking, “So what?” Well, researchers speculate that continued use of porn over time, especially starting at younger ages, makes it such that we actually lose willpower. The more we watch porn, the more difficult it is for men to say to no to watching porn because of the strong craving they feel.

This is not the kind of men most men want to be. We want to enjoy our passions, not be enslaved to them.

Related: Brain Chemicals and Porn Addiction

4. Porn makes violence sexy.

According to research by Dr. Dolf Zillmann and Dr. Jennings Bryant, the more porn one is exposed to, the more likely one is willing to trivialize rape. In their experiments, after watching just five hours of pornographic films stretched over a six-week period, subjects were willing to cut the sentencing of an accused rapist nearly in half, compared to those who had not watched pornography at all.

Those who watched more porn were also likely to believe that practices like sadomasochism were two to three times more common in general society than those who had not seen porn. Of course porn doesn’t make most consumers into sexually violent people, it does train men to embrace a culture of objectification, reinforcing a belief that women exist to give sexual pleasure to men. Again, is this the kind of men we want to become?

Let me make an appeal to men:

if your goal is to become a man whose standard of beauty is shaped by the one you love…

if your goal is to feel a personal sense of worth and validation based on your most valuable relationships…

if your goal is to be a man of self-mastery, not enslaved to your passions…

and if your goal is to treat women as people to be served and loved, not see them as objects for your pleasure…

…then consuming porn will take you in the opposite direction.