Validation of laughter for diagnosis and evaluation of depression.
BACKGROUND
In the medical field, laughter has been studied for its beneficial effects on health and as a therapeutic method to prevent and treat major medical diseases. However, very few works, if any, have explored the predictive potential of laughter and its potential use as a diagnostic tool.


METHODS
We registered laughs of depressed patients (n=30) and healthy controls (n=20), in total 934 laughs (517 from patients and 417 from controls). All patients were tested by the Hamilton Depression Rating Scale (HDRS). The processing was made in Matlab, with calculation of 8 variables per laugh plosive. General and discriminant analysis distinguished patients, controls, gender, and the association between laughter and HDRS test.


RESULTS
Depressed patients and healthy controls differed significantly on the type of laughter, with 88% efficacy. According to the Hamilton scale, 85.47% of the samples were correctly classified in males, and 66.17% in women, suggesting a tight relationship between laughter and the depressed condition.


CONCLUSIONS
(i) The compilation of humorous videos created to evoke laughter implied quite variable chances of laughter production. (ii) Some laughing subjects might not feel comfortable when recording. (iii) Evaluation of laughter episodes depended on personal inspection of the records. (iv) Sample size was relatively small and may not be representative of the general population afflicted by depression.


CONCLUSIONS
Laughter may be applied as a diagnostic tool in the onset and evolution of depression and, potentially, of neuropsychiatric pathologies. The sound structures of laughter reveal the underlying emotional and mood states in interpersonal relationships.
Aragon Institute of Health Science (IACS), Zaragoza, Spain; Aragon Health Research Institute (IIS Aragón), Zaragoza, Spain. Electronic address: jnavarro.iacs@aragon.es.
J
J
Navarro
Aragon Institute of Health Science (IACS), Zaragoza, Spain; Aragon Health Research Institute (IIS Aragón), Zaragoza, Spain.
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R
del Moral
Aragon Institute of Health Science (IACS), Zaragoza, Spain; Aragon Health Research Institute (IIS Aragón), Zaragoza, Spain.
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Alonso
Aragon Institute of Health Science (IACS), Zaragoza, Spain; Aragon Health Research Institute (IIS Aragón), Zaragoza, Spain.
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Loste
Aragon Research Group of Primary Care, Preventive Activities and Health Promotion Network (REDIAPP) (G06/170), IACS, Zaragoza, Spain; Aragon Health Service, Psychiatry Department, Miguel Servet Hospital, Zaragoza, Spain.
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J
Garcia-Campayo
Department of Applied Mathematics (Biomathematics), Faculty of Biological Sciences, Complutense University of Madrid, 28040 Madrid, Spain.
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Lahoz-Beltra
Aragon Institute of Health Science (IACS), Zaragoza, Spain; Aragon Health Research Institute (IIS Aragón), Zaragoza, Spain. Electronic address: pcmarijuan.iacs@aragon.es.
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Marijuán
D016022:Case-Control Studies; D003863:Depression / Q000175:diagnosis* / Q000523:psychology*; D005260:Female; D006801:Humans; D007845:Laughter / Q000523:psychology*; D008297:Male; D011569:Psychiatric Status Rating Scales; D015203:Reproducibility of Results
Depression; Laughter; Neuropsychiatry; Plosives; Sound structures