Identifying Patients with Therapy-Resistant Depression by using Factor Analysis

Abstract

Introduction: Attempts to identify the factor structure in patients with treatment-resistant depression have been very limited.

Methods: Principal component analysis was performed using the baseline datasets from 3 add-on studies [2 with repetitive transcranial magnetic stimulation and one with transcranial pulsed electromagnetic fields (T-PEMF)], in which the relative effect as percentage of improvement during the treatment period was analysed.

Results: We identified 2 major factors, the first of which was a general factor. The second was a dual factor consisting of a depression subscale comprising the negatively loaded items (covering the pure depression items) and a treatment resistant subscale comprising the positively loaded items (covering lassitude, concentration difficulties and sleep problems). These 2 dual subscales were used as outcome measures. Improvement on the treatment resistant subscale was 40% in the active treatment group compared to 17–30% improvement in the sham treatments.

Discussion: It is possible to describe patients with therapy-resistant depression by a factor structure. Both rTMS and T-PEMF had a clinical effect on the factor-derived scales when compared to sham treatment.

References

• 1 Allerup P. Statistical analysis of rating scales.  Danish Institute of Educational Research, Copenhagen 1986; 
• 2 Avery DH, Holtheimer PE, Fowaz W. et al . Controlled study of repetitive transcranial magnetic stimulation in medication-resistant major depression.  Biol Psychiatry. 2005;  59 187-194
• 3 Bagby RM, Ryder AG, Schiller DR. et al . The Hamilton depression rating scale: has the gold standard become a lead weight?.  Am J Psychiatry. 2004;  161 2163-2177
• 4 Bech P, Allerup P, Gram LF. et al . The Hamilton depression scale. Evaluation of objectivity using logistic models.  Acta Psychiatr Scand. 1981;  63 290-299
• 5 Bech P, Allerup P, Reisby N. et al . Assessment of symptom change from improvement curves on the Hamilton depression scale in trials with antidepressants.  Psychopharmacology. 1984;  84 276-281
• 6 Bech P, Allerup P, Maier W. et al . The Hamilton scales and the Hopkins symptom checklist (SCL-90). A cross-national validity study in patients with panic disorders.  Br J Psychiatry. 1992;  160 206-211
• 7 Bech P. The Bech, Hamilton and Zung scales for mood disorders: screening and listening. Springer Berlin. 2nd Edn; 1996
• 8 Bech P. Applied psychometrics in clinical psychiatry: The pharmacopsychometric triangle.  Acta Psychiatr Scand. 2009;  120 400-409
• 9 Bretlau LG, Lunde M, Lindberg L. et al . Repetitive transcranial magnetic stimulation (rTMS) in combination with escitalopram in patients with treatment-resistant major depression. A double-blind, randomised, sham-controlled trial.  Pharmacopsychiatry. 2008;  41 41-47
• 10 Burt T, Lisanby SH, Sackeim HA. Neuropsychiatric application of transcranial magnetic stimulation: a metaanalysis.  Int J Neuropsychopharmacol. 2002;  5 73-103
• 11 Child D. The Essentials of Factor Analysis. 3rd Edn. Cassel Educational, London; 2006
• 12 Fekadu A, Wooderson S, Donaldson C. A multidimensional tool for quantifying treatment resistance to depression: The Maudsley staging method.  J Clin Psychiatry. 2009;  70 177-184
• 13 Hamilton M. Development of a rating scale for primary depressive illness.  Br J Soc Clin Psychol. 1967;  6 278-296
• 14 Hamilton M. Diagnosis and rating of anxiety.  Br J Psychiatry. 1969;  (Special publ) 76-79
• 15 Hamilton M. Clinical evaluation of depressions: Clinical criteria and rating scales, including a Guttman Scale. In Gallant DM, Simpson GA (eds). Depression: Behavioural, biochemical, diagnosis and treatment concepts. New York, Spectrum Publication; 1976: 155-179
• 16 Kline P. The handbook of psychological testing. London, Routledge; 1993
• 17 Kørner A, Nielsen BM, Eschen F. et al . Quantifying depressive symptomatology: inter-rater reliability and inter-item correlations.  J Affec Dis. 1990;  20 143-149
• 18 Lauritzen L, Odgaard K, Clemmesen L. et al . Relapse prevention by means of paroxetine in ECT-treated patients with major depression: a comparison with imipramine and placebo in medium-term continuation therapy.  Acta Psychiatr Scand. 1996;  94 241-251
• 19 Licht RW, Qvitzau S, Allerup P. et al . Validation of the Bech-Rafaelsen melancholia scale and the Hamilton depression scale in patients with major depression; is the total score a valid measure of illness severity?.  Acta Psychiatr Scand. 2005;  111 144-149
• 20 Marli GS, Parker GB, Greenwood J. Structural and functional models of depression: from sub-types to substrates.  Acta Psychiatr Scand. 2005;  111 94-105
• 21 Martiny K, Lunde M, Bech P. Controlled study of pulsed magnetic fields (PEMF) in medication-resistant major depression.  Eur Neuropsychopharmalogy. 2009;  19 478
• 22 Martiny K, Lunde M, Bech P. Transcranial low voltage pulsed electromagnetic fields (T-PEMF) in patients with treatment-resistant depression.  Biological Psychiatr. 2010;  68 163-169
• 23 Montgomery SA, Åsberg M. A new depression scale designed to be sensitive to change.  Br J Psychiatry. 1979;  134 382-389
• 24 Nolen WA, Zohar J, Roose SP. (Eds). Refractory depression. Current strategies and future directions. Chichester, John Wiley; 1994
• 25 Parker GB, Malhi GS, Crawford JG. et al . Identifying ‘paradigm failures’ contributing to treatment resistant depression.  J Affect Disord. 2005;  87 185-191
• 26 Paykel ES. Achieving gains beyond response.  Acta Psychiatr Scand. 2002;  106 (Suppl. 415) 12-17
• 27 Rahbek UL, Tritsaris K, Dissing S. Interactions of low frequency, pulsed electromagnetic fields with living tissue: biochemical responses and clinical results.  Oral Biosci Med. 2005;  2 29-40
• 28 Sackeim HA. The definition and meaning of treatment-resistant depression.  J Clin Psychiatry.. 2001;  62 (Suppl. 16) 10-17
• 29 Uher R, Farmer A, Maier W. Measuring depression: comparison and integration of three scales in GENDEP-study.  Psychol Med. 2008;  289-300

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