A group of illnesses that are difficult to assess objectively, comprising such conditions as fibromyalgia, chronic fatigue syndrome, attention-deficit hyperactivity disorder, whiplash injury, and last but not least a multitude of somatoform disorders, has become a growing concern to Western health care systems and insurance industries. Thus far, the medical literature has failed to provide informative overviews of this group, which at first glance admittedly seems to be rather heterogeneous. If at all, the disorders have been grouped together under the term ,,controversial illnesses" to differentiate them from other diseases. The insurance industry - and claims departments, in particular - are increasingly having to deal with this rapidly growing phenomenon, which affects not only life business, but also health, worker's compensation and motor third-party liability. When paying compensation and settling claims, insurers are often left with a feeling that the illness may have been ,,imaginary" or aggravated. Is there a common basis for this new disorder mega-trend - independent of the recognition of the conditions by medical associations? This article aims at providing an overview of the common characteristics of the group of disorders, including a description of the key physical, psychological and social aspects. In particular, it is intended to deepen insurers' understanding of the risks arising from social change. The article also examines the disorder prevalence in Western societies and the possible causes of the significant increase.