Christopher Foster, the super-salesman turned entrepreneur suspected of murdering his wife, daughter, dogs and horses before burning his Shropshire mansion, was described by his friends as being a family man who cared so much about his family's safety that he had installed hugely expensive security measures to foil a plot to kidnap his daughter.

His colleagues, meanwhile, were reported to have described him as a great companion, a larger-than-life character who laboured from dawn to dusk, and an outstanding salesman. Apparently he was a man with sudden, sometimes inspired, ideas. One was a new form of insulation for pipes used in the oil industry. It made him a fortune that he subsequently lost, and is now reported to be making an even greater fortune for those who have taken over Foster's idea.

It was reported that Foster had shown evidence of a personality as remarkable as his lifestyle - four luxury cars, one an Aston Martin, a pleasant 18th-century country house recently done up, all despite estimated debts of up to £2 million. Unfortunately, although commented on, it wasn't recognised for what it may have been: the early symptoms of bipolar disorder, or manic depression.

In industry and commerce some of the most brilliant salesmen have symptoms suggestive of bipolar disorder manqué. Frequently the management understands that this rather special salesperson is not as others, but are prepared to tolerate and overlook periods of depression and lethargy because of his or her genius and innovatory powers when in a different frame of mind. Those with hypomania can be an inspiration in the office and deserve reward for their talents, but this recognition doesn't usually include the chance to manage accounts.

Christopher Foster loved his family and lifestyle. If initial police theories are confirmed, it seems that he couldn't bear to lose either. Others in his situation and with their temperaments in a depressive phase kill their families to spare them the miseries of this supposedly hopeless world.

Many authors are condemned for populating their books with stereotypes that make for an uninspiring read. Regrettably, in reality, stereotypes abound and the nature of our characters determines our drift towards professions that fit them. Lawyers, actors, politicians and even teachers or parsons need to captivate their audiences to keep them awake while absorbing information imparted by the speaker. Many have a theatrical and histrionic element to their personalities that livens up their delivery.

Old-fashioned medical practice suited people who were co-dependent and, as a result, many practitioners had an ego that needed constant stroking by grateful patients. A large percentage of older doctors and nurses had co-dependent personalities and if they didn't receive the feedback they hoped for, felt unfulfilled and depressed. Many painters, poets, writers and other creative workers are drawn to the mystical, metaphysical and esoteric, and could be described as having a schizotypal personality disorder.

The role of families and other carers in the treatment of patients with psychiatric symptoms was discussed at a recent meeting in Barcelona organised by the European Federation of Associations of Families of People with Mental Illnesses. Once the patient's problem has moved from a personality disorder to a definable psychosis (ie, his or her behaviour is divorced from reality), his or her family and other carers, including the family doctor and community psychiatric services, can be essential in persuading the patient to take his or her medication. This may be stopped because of sideeffects, because the patient feels better, or because he or she resents needing medication and loathes the stigma attached to mental disease. Few patients realise that each relapse may cause further damage and reduce the chance of a good response.

Whatever the nature of the medication, its continued use is the mainstay of treatment and the prevention of relapse. The carer's role takes a psychological and physical toll on their health. Many show stress symptoms and, recent research indicates, a weakened immune system.

When manic or hypomanic, a patient with bipolar disorder shows variable degrees of overactivity, euphoria, fast-talking exuberance and sleeplessness without evidence of tiredness. When seriously depressed - and the mood change, frequently precipitated by alcohol or drugs, can be sudden - there may be paranoid thoughts. Was Christopher Foster really in danger of kidnapping, or were his fears exaggerated to the point of delusion?