может у кого-то имеется научный материал по теме ониомании?

Насчёт немецких - смотрите - их не так много, а английских - уйма. Вот некоторые из Медлайна (можете сами всё найти) :
http://en.wikipedia.org/wiki/Oniomania
[Compulsive buying disorder: a review and a case vignette]

Tavares H, Lobo DS, Fuentes D, Black DW.

Rev Bras Psiquiatr. 2008 May;30 Suppl 1:S16-23. Epub 2008 Jan 31. Review. Portuguese.
PMID: 18278383 [PubMed - indexed for MEDLINE]
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2.Compulsive buying disorder: a review of the evidence.

Black DW.

CNS Spectr. 2007 Feb;12(2):124-32. Review.
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3.Compulsive buying: descriptive characteristics and psychiatric comorbidity.

Christenson GA, Faber RJ, de Zwaan M, Raymond NC, Specker SM, Ekern MD, Mackenzie TB, Crosby RD, Crow SJ, Eckert ED, et al.

J Clin Psychiatry. 1994 Jan;55(1):5-11.
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4.[Pathological buying -- a literature review]

Müller A, Reinecker H, Jacobi C, Reisch L, de Zwaan M.

Psychiatr Prax. 2005 Jan;32(1):3-12. Review. German.
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5.[Treatment of compulsive buying]

Mueller A, de Zwaan M.

Fortschr Neurol Psychiatr. 2008 Aug;76(8):478-83. Review. German.
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6.Family history and psychiatric comorbidity in persons with compulsive buying: preliminary findings.

Black DW, Repertinger S, Gaffney GR, Gabel J.

Am J Psychiatry. 1998 Jul;155(7):960-3.
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7.Study of compulsive buying in depressed patients.

Lejoyeux M, Tassain V, Solomon J, Adès J.

J Clin Psychiatry. 1997 Apr;58(4):169-73.
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8.Kleptomania, compulsive buying, and binge-eating disorder.

McElroy SL, Keck PE Jr, Phillips KA.

J Clin Psychiatry. 1995;56 Suppl 4:14-26; discussion 27. Review.
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9.Cognitive behavioral therapy for compulsive buying disorder.

Mitchell JE, Burgard M, Faber R, Crosby RD, de Zwaan M.

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10.Phenomenology and psychopathology of uncontrolled buying.

Lejoyeux M, Adès J, Tassain V, Solomon J.

Am J Psychiatry. 1996 Dec;153(12):1524-9. Review.
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11.Characteristics of 34 adults with psychogenic excoriation.

Arnold LM, McElroy SL, Mutasim DF, Dwight MM, Lamerson CL, Morris EM.

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12.Oniomania--successful treatment with fluvoxamine and cognitive-behavioral psychotherapy.

Marcinko D, Karlović D.

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13.A randomized, controlled trial of group cognitive-behavioral therapy for compulsive buying disorder: posttreatment and 6-month follow-up results.

Mueller A, Mueller U, Silbermann A, Reinecker H, Bleich S, Mitchell JE, de Zwaan M.

J Clin Psychiatry. 2008 Jul;69(7):1131-8.
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14.