Should married men and women have friends of the opposite gender? I don’t think it’s smart.

Of course, this is controversial. Many would say, “You’re being prudish. It’s no big deal.” But I’ve heard too many clients tell me, “This person and I became friends outside of my marriage. Pretty soon we were having an affair.”

Each of us has acquaintances of the opposite gender. We have co-workers, spouses of friends, neighbors, people we engage in sports with. Most of these interactions are appropriate and cause no repercussions for our relationships.

Trouble brews when we develop deeper attractions for one of those people. We move from a platonic and cordial, “Hi-how-are-you?” kind of association to a longing to please each other.

These relationships are no longer mere friendships. They’ve definitely crossed the line.

Unfortunately, that line can be murky. Some folks aren’t even aware that it exists. It’s that very inattention to what they’re doing that sounds the death knell for lots of couples.

The problem arises with the broad definition of the word “friend.” According to common usage, a friend may be someone you wave to in your spin class or an on-again-off-again boyfriend you’re not ready to commit to. A guy may want to break up with his girlfriend but tell her, “I hope we can still be friends.” I’ve even heard couples who were passionately in love refer to themselves as friends.

Such imprecise communication invites relational mayhem. We’re dishonest about what we’re doing. Our behaviors and words don’t match up.

Let’s be clear: Friends are people we have lunch with. We send them cards on their birthdays. We go to movies together.

We don’t have sex with friends. We have sex with our lovers. When any form of sexual attraction creeps into our platonic relationships, we’ve shifted into different gears. We must admit to ourselves what we’re doing and stop at once or suffer the consequences.

This is why I don’t recommend maintaining friends of the opposite gender outside of marriage. Red flags start waving whenever I hear about them. They may be innocent enough in their intent. Still, the potential for danger is too great.

Of course, I have real fondness for many of my girlfriends’ husbands. I’m friendly with loads of guys I know. But the relational boundaries are rock solid. They’re my own version of the Great Wall. There’s no room for ambiguity.

The stakes are way too high.

Tips for assessing opposite-sex friendships

Wondering if your relationship has crossed the line? Here are sure-fire signs:

• You dress in ways that make you more attractive to the other person.

• You think about the person when you’re apart.

• You eagerly look forward to your next meeting.

• You discuss topics you wouldn’t share with your spouse.

• You are friends on Facebook and you wouldn’t want your spouse to find out.

• You text each other throughout the day.

• You feel uneasy about what you are doing.

• Your spouse would be upset by your contact with the person.

• Your relationship draws your attention away from your spouse.

If you’re already too involved with another person, take these steps immediately:

• Tell the person today that it’s over. Explain in no uncertain terms that you are ending the relationship. Keep the communication brief and focused. Anything longer will only weaken your resolve.

• Get off Facebook and all social networking sites. These allow you to have private contact with potentially inappropriate people. They’re a bad choice for you.

• Stop responding to any of the other person’s emails or texts. Delete any forms of communication without reading it. If he or she continues in spite of your protests, change your email address or cell phone number.

• Change your schedule so that you’re no longer in contact. Go to a new gym or take a different college class. This may seem like an imposition, but the survival of your primary relationship is at stake.

• Reconnect with your spouse. Go out to dinner. Invite friends to a concert. Arrange for an intimate evening. Weakened marital bonds may have contributed to your initial behavior. Now’s the time to shore them up so your relationship will survive.

Linda Lewis Griffith is a local marriage and family therapist. For information or to contact her, visit lindalewisgriffith.com