"Toxic" is overused online, often stretched to cover any uncomfortable dynamic. The ten patterns below are different — each has been measured in longitudinal studies against wellbeing outcomes, and each carries a specific mechanism worth knowing. The point isn't to label people; it's to see clearly which dynamics erode happiness over time so you can decide what to do about them.

1. The chronic critic

John Gottman's four-decade research identified criticism (as opposed to complaint) as one of the four strongest predictors of relationship dissolution. The mechanism: character attacks shift the perceived ratio of positive to negative interactions below the 5-to-1 threshold that healthy relationships maintain.

2. The stonewaller

Another of Gottman's "four horsemen." Emotional withdrawal during conflict drives physiological stress in the other partner and prevents resolution. Over months, the pattern is strongly associated with depression and lower life satisfaction.

3. The scoreboard-keeper

Tracking favours owed and grievances filed — researchers call this "exchange orientation" — correlates inversely with relationship satisfaction in both friendships and romantic bonds. Intimacy requires at least partial amnesia about who did what last.

4. The person who can never be wrong

Defensive rigidity — the inability to accept influence — predicts divorce with high accuracy in Gottman's data. In friendships it predicts gradual drift. The cost isn't the defensiveness itself; it's the message "I am not a person you can reach."

5. The drainer

One-way emotional support relationships — where you listen, they never ask — show up in happiness research as a chronic low-level stressor. A little of this is normal in any relationship; a pattern of it across years correlates with measurable increases in cortisol for the giver.

6. The gaslighter

Chronic reality-denial ("that didn't happen", "you're imagining it") is associated with anxiety disorders and long-term erosion of self-trust. This one is serious; the science backs taking it seriously.

7. The contempt-holder

The strongest single predictor of divorce in Gottman's data. Contempt — eye-rolling, mockery, sarcasm with bite — signals that one partner sees the other as beneath them. Its presence in a relationship predicts immune-system impact in the receiving partner.

8. The isolator

Relationships that gradually cut you off from other relationships — monitoring calls, resenting outside friendships, creating tension when you want to see family — correlate with some of the worst wellbeing outcomes in the literature. Your social network is protective; a partner who erodes it is removing protection.

9. The intermittent reinforcer

Alternating warmth and withdrawal is psychologically similar to a variable-ratio reinforcement schedule — the same one that makes slot machines addictive. Research shows these dynamics are harder to leave than consistently hostile ones, and they correlate with elevated anxiety scores.

10. The quietly unequal partner

Sustained imbalance in effort, care, and emotional labour doesn't feel toxic day-to-day but accumulates. Studies on married couples find this pattern is one of the more robust correlates of lower life satisfaction for the over-giving partner, even when no other toxic marker is present.

Some of these are fixable with a clear conversation. Some aren't. The science is useful here mostly for seeing what's happening clearly — what to do about it once you've seen it is still a human decision, not a scientific one.