Lurking behind any discussion of mens' stress is a large caveman, swinging his heavy club.

The most common perception of stress is the 'fight or flight' scenario, and the story goes something like this. A caveman is confronted by an angry Mastodon: he either needs to club it to death, or run for his life. A quick surge in the 'stress hormone' adrenaline allows him to act by strengthening his heartbeat, widening his airways and redirecting blood to his muscles.

But there are two problems with this Neanderthal model. Firstly, the riskiest animals our predecessors had to confront were rabbits and deer, not elephants and tigers. In fact, our hairy forefathers spent most of their time collecting berries and roots with their children, aunties, and pals. Just like us, the caveman never stood alone in front of wild animals - unless there had been some kind of terrible mistake.

The second error is to try to relate stress solely to adrenaline. Although the physical effects of frights and acute (short-term) stress are caused by adrenaline, this hormone doesn't enter the brain. Longer-term stress relates to a range of other hormones and brain neurotransmitters.

• Serotonin- involved in regulation of sleep, appetite and mood.
• Dopamine- part of the brain's 'reward system'.
• Noradrenaline- involved in regulating energy and drive.
• GABA- has a general sedative effect.
• Glutamate- tends to activate nerve cells.
• CRF- increases steroid levels.

Steroid levels rise during long-term stress, and it seems likely that it's the body's own natural steroids - not adrenaline - that cause most stress-related health problems. Long-term, increased steroid levels have been linked to impaired immunity, and illnesses like heart disease, cancer and depression.

These chemicals would have affected the caveman just as they do us. Our macho image of 'fight or flight' stress is wrong, because being stressed isn't about a beating heart, or a dry mouth. The signs are much more subtle - and they can't be tackled with a club and a spear.

• Constant fatigue and irregular sleep patterns.
• Poor concentration and short-term memory.
• Introspection increases and is accompanied by neglect of the family and personal appearance.
• Constant repetition of the same actions.
• Increased irritability.

But even if you don't recognize the stress-symptoms listed here, don't presume you're fit and well. Everyone's reaction is idiosyncratic, and it can be astonishingly difficult to recognize at the time.

Fortunately, your own pattern of stressed-out behaviors will tend to recur each time you get frazzled. If stress makes you bite your fingernails to the quick (like Samuel Johnson), or gorge on junk food (like Bill Clinton) or drink more than you should (like most of us), it's likely that you'll start doing the same thing again next time.

There are medical treatments that help stress-related conditions like depression and anxiety, but nothing that's really effective for stress itself. This is quite appropriate - stress isn't an illness, it's an important part of life. Learning to cope with - and even enjoy - stress is the best way. Cavemen, lay down your clubs.