Was it really a faux pas, or a simple piece of devilment?

When a Hollywood reporter revealed the conclusion of the hit CIA drama Homeland to ardent fan Jennifer Lawrence while she was on the red carpet with its star Damian Lewis, the actress seemed genuinely upset and said she felt like her heart "just fell out" (I think we know what she meant).

She had already told the interviewer she hadn't seen it; both the recipient and the imparter of the news were apparently devastated. The reporter apologised, but I wonder whose life was more damaged as a result of the spoiler.

It has to be said that some secrets are more potent than others; compared to some, the Homeland gaffe was nothing. The urge to reveal a secret, regardless of motivation, can be overwhelming in some people, which is why they should never be trusted with one in the first place. Many a friendship has ended when that trust is broken, whether through drink or spite or sheer carelessness.

A genuine mistake can lead to the most crippling remorse, but it can also give enormous relief, especially if the secret being withheld is helping prolong behaviour that is damaging others. The fallout from French President Francois Hollande's "secret affair" with an actress, for example, put his partner in hospital.

Some psychologists believe that withholding a secret can hurt. One of the most common mantras of Alcoholics Anonymous, for example, is "you're only as sick as your secrets". It's true that one of the hallmarks of addiction is deception.

But the burning question is how to tell the difference between the kind of secret that should be kept and the kind that shouldn't.

Psychologist Alex Lickerman suggests a good rule of thumb would be this: the ones that shouldn't be kept are those that allow us to behave in a way that causes harm to others or to ourselves (alcohol, drugs, gambling) as well as infidelities (to spouses, business partners, friends and so on). Confessing such secrets to the right people, he suggests, makes it much harder for the harm caused by such secrets to continue. But if someone cheats on their partner once, regrets it, and resolves never to do it again, would revealing it cause more good than harm?

I happen to know a friend of a friend of a friend who's harbouring a pretty juicy secret. I can't tell you what it is, and I won't; but keeping mum is agony. Sometimes life is easier when you have no secrets.