The present invention provides a method of treatment or management of various adaptogenic conditions, such as, stress in mammals, more particularly, humans, comprising administering Withania somnifera plant extract. A high purity extract composition comprising withanolide glycosides, oligosaccharides, withanolide aglycones and a minimum level of polysaccharides, and a pharmaceutically, veterinary or nutritionally acceptable carrier(s) is disclosed. Preferably, the composition of the present invention can be devoid of any alkaloids or contains trace levels of alkaloids. The method of treatment or management of stress administering the composition comprising Withania somnifera of the present invention does not suffer from any one of the abovementioned side effects even after prolonged use. A method of preconditioning a mammalian patient to improve the patient's resistance and reaction to subsequently encountered stress is described.