Here is a very recent study and write up:
http://www.ncbi.nlm.nih.gov/pubmed/22825366
http://celiacdisease.about.com/od/glutenintolerance/a/Gluten...
And here is a well-cited summary of the facts:
Symptoms of gluten sensitivity may include bloating, abdominal discomfort, pain, or diarrhea; or it may present with a variety of extraintestinal symptoms including headaches and migraines, lethargy and tiredness, attention-deficit disorder and hyperactivity, autism and schizophrenia, muscular disturbances as well as bone and joint pain. [1][2][3][4]
Whilst the research surrounding gluten sensitivity is still very much emerging, coeliac disease is a well-defined condition. It is a lifelong autoimmune condition characterised by the chronic inflammation of the intestine... In comparison, in a recent clinical paper, gluten sensitivity was defined as ‘one or more of a variety of immunological, morphological or symptomatic manifestations that may also be shared by coeliac disease and irritable bowel syndrome (IBS) [5]. In cases where there is reactivity to gluten, yet coeliac disease and wheat allergy are eliminated as possibilities, gluten sensitivity may be considered. Whilst the general clinical picture for gluten sensitivity is similar to coeliac disease in particular, it is usually less severe and neither anti-tissue transglutaminase antibodies nor autoimmune comorbidities are found. It is believed that approximately 40-50% of gluten sensitivity patients may have IgG or IgA anti-gliadin antibodies (AGA) [6][7]. There is also a study identifying approximately 50% of gluten sensitivity patients, few more than the general population, carry either HLA DQ 2 or 8 [8].
[1] Sapone A et al. Differential mucosal IL-17 expression in two gliadin-induced disorders: gluten sensitivity and the autoimmune enteropathy celiac disease. International Archives of Allergy and Immunology. 2010;152:75-80; Ford RP. The gluten syndrome. A neurological disease. Medical Hypotheses. 2009; 73 (3):438-440 [2] Elder JH et al. The gluten-free, casein-free diet in autism: results of a preliminary double-blind clinical trial. Journal of Autism and Developmental Disorders. 2006;36(3):413-420 [3] Dickerson F et al. Markers of gluten sensitivity and celiac disease in recent onset psychosis and multi-episode schizophrenia. Biological Psychiatry. 2010;68(1):100-104 [4] Hadjivassiliou M et al. Myopathy associated with gluten sensitivity. Muscle Nerve. 2007;35:443-450 [5] Verdu EF, Armstrong D, Murray JA. Between celiac disease and irritable bowel syndrome: The ‘No Man’s Land’ of Gluten Sensitivity. The American Journal of Gastroenterology. 2009;104(6):1587-1594 [6] Sapone A et al. (2010). Differential mucosal IL-17 expression in two gliadin-induced disorders: gluten sensitivity and the autoimmune enteropathy celiac disease. International Archives of Allergy & Immunology; 152: 75-80 [7] Bizzaro N et al. (2010) Cutting edge issues in celiac disease and in gluten intolerance. Clinical Reviews in Allergy & immunology. [8] Sapone A et al. (2010). Differential mucosal IL-17 expression in two gliadin-induced disorders: gluten sensitivity and the autoimmune enteropathy celiac disease. International Archives of Allergy & Immunology; 152: 75-80.