Table 1.
Summary of selected studies – Electrodermal activity (EDA) and suicidal behavior
| AUTHORS (COUNTRY AND YEAR) | SUBJECTS (DIAGNOSIS; AGE; MALE/FEMALE) AND CONTROLS (AGE; MALE/FEMALE) | MEASURES | MAIN STUDY FINDINGS | STUDY DESIGN (QUALITY1) |
|---|---|---|---|---|
| Crowell et al. (USA, 2005) | − 23 parasuicidal adolescent girls, age 14–18, − 23 age-matched controls. |
EDA recordings during the last minute of a 10-min resting baseline and for 10 min of recovery following the end of a sad movie. | No significant differences on measures of EDR between parasuicidal girls and healthy controls. | Case-control(3) |
| Edman et al. (1986) | 35 drug-free, suicidal inpatients (mean age 41 years; 63% females): − 24 inpatients after a suicide attempt; − 11 patients with suicidal ideation. |
SCL and habituation of the SCR. | No differences in the SCL. Tendency to lower figures in NS.SCR in patients who used violent suicide methods. All violent attempters (at baseline and follow-up) were fast habituators. Lowest frequency of fast habituators in patients with suicidal ideation. |
Cross-sectional |
| Jandl et al. (Germany, 2009) | MDD inpatients divided in 3 groups: − 16 with history of ‘hard attempted suicide’ (e.g., hanging, stabbing) (47.3±11.9 years; 56% females); − 16 with a history of ‘soft attempted suicide’ (e.g. poisoning) (49.8±8 years; 69% females); − 18 no attempted suicide (47.9±11.6 years; 67% females). |
NS.SCR frequency, SCR amplitude and EDA Habituation Rate measured during an auditory habituation paradigm. |
Significantly lower EDA habituation rate in both suicide attempters groups. No difference among the 3 groups in SCR amplitude or NS.SCR frequency. Women showed faster habituation. |
Cross sectional |
| Keller et al. (Germany, 1991) | − 23 patients with suicide attempt divided into violent and non-violent method (violent, N=14, 41.4±9.5 years, 64% females; non-violent, N= 9, 37.2±9.7 years, 66.6% females). − Age and sex matched groups (non-suicidal depressed patients/patients with suicidal thoughts. |
Number of stimuli until habituation, nonspecific SC reactions, height of first amplitude and SCL measured during an habituation experiment. | All patients who had used a violent method and patients who committed suicide in the year following the experiment were fast habituators. No difference in EDA between non-suicidal patients, those with suicidal thoughts or suicide attempts. |
Case-control (4) |
| Sarchiapone et al. (Europe, 2017) | -1573 patients with a primary clinical diagnosis of depression, either currently depressed or in remission. | − ElectroDermal Orienting Reactivity (EDOR Test) | It is hypothesized that the EDOR Test will identify electrodermal hyporeactive depressed patients with a high suicidal proneness. Patients who reveal strong death intent are expected to be hyporeactive at the EDOR test, in most cases; non-hyporeactive patients are expected to have suicide attempts with strong death intent in a minority of cases. |
Multicentric/ Study protocol |
| Spiegel (US, 1969) | Inpatients including: - 16 controls with no history of suicide threats or attempts and denying current suicidal thoughts; - 15 inpatients with suicide threats or preoccupations but no history of attempts; - 13 attempters with a history of one or more suicide attempts. |
GSR First two sessions: word association. 4 days later, a series of words at irregular intervals, recording skin resistance changes. |
Relatively low reactivity of threateners might be a function of depression. Threateners were the least reactive in terms of GSR to the word “suicide” Significant positive association between magnitude of GSR and intensity of affective meaning assigned to the concept “suicide” in all patients. |
Crossover |
| Thorell (Sweden, 1987) Thorell et al. (1987a) Thorell et al. (1987b) |
− 59 in- and out-patients with major depressive episode and dysthymic disorders (42±13.2 years; 54% females); − 59 mentally and somatically healthy subjects (42.4±13.3 years; 54% females) |
SCL at the onset of the first stimulus, mean SC fluctuation rate (SCFr) per minute, SCR magnitude (SCRm) to the first stimulus, SCR rate (SCRr), and index of SC nonresponding (SCRi). | Significantly lower central SCL, SCRm, SCRr, and SCRi, but not SCFr and habituation values in patients than in controls. Considering medications, no statistically significant difference in any EDA variable. No significant difference in any EDA variable among dysthymic disorder vs major depressive episode and melancholic vs non-melancholic major depressive episode. Patients with endogenous depression had significantly lower SCL, SCRr, and SCRi. Patients with a high level of inhibition showed significantly lower SCL and SCRi. Suicidal behavior related to low electrodermal responsivity (EDR) and low stimulus-unrelated phasic activity, but unrelated to tonic EDA. Extreme hyporesponsivity in the suicide attempters was observed irrespective of whether the attempt had been made previously or during the current depression. |
Case-control (5) |
| Thorell et al. (2009) | − 279 depressed patients − 59 healthy subjects |
Habituation of the electrodermal response |
Sensitivity 96.6% and specificity 92.9% of electrodermal hyporeactivity for suicide and 83.3% and 92.7%, respectively, for suicide and⁄or violent attempts | Meta-analysis |
| Thorell et al. (Germany, 2013)2 | 783 depressive patients (126 bipolar patients; 539 unipolar patients; 118 with other diagnoses) (42.9±11.5; 58% females): − 32 violent suicide; − 4 nonviolent suicide; − 84 violent suicide attempt; − 103 nonviolent suicide attempt; − 560 other or no suicidal behavior. |
Habituation of electrodermal responses measured during an auditory habituation paradigm. | Prevalence of electrodermal hyporeactivity was high and highest (80%) among bipolar patients and was independent of severity of depression, trait anxiety, gender and age. Sensitivity and specificity for suicide, and for suicide and violent suicide attempt were 83%, 98% and 74%, 88%, respectively. Hyporeactivity was stable, while reactivity changed into hyporeactivity in a later depressive episode. |
Cohort (7) |
| Wolfersdorf et al. (Germany, 1996) | − 11 patients with personality disorders who attempted suicide (23±4 years; 100% females); − Depressed non-suicidal patients (100% females); − Depressed suicide attempters (100% females); − Schizophrenic non-suicidal patients (100% females); − Schizophrenic suicide attempters (100% females). |
SCL, number of NS.SCR, habituation of the SCR | Significant differences in EDA values between women with personality disorders who attempted suicide and non-suicidal women suffering from depression. No difference between personality disorder and depressive patients who attempted suicide . No significant differences in EDA values in a habituation study between personality disorder patients and schizophrenic women with or without histories of suicide attempts. |
Cross-sectional |
| Wolfersdorf et al. (Germany, 1999) | − 30 depressed violent suicide completers (mean age 43.8 years; 57% females); − Age and sex matched non-suicidal depressed patients; − Age and sex matched depressed patients with suicidal ideations; − Age and sex matched depressed patients with suicide attempts. |
Number of stimuli up to habituation (habituation score, HS), SCL and amplitude of SCR after the first stimulus measured during a habituation experiment using auditory stimuli. | Depressed patients who died by suicide showed significantly lower HS, first amplitude of the SCR and SCL than non-suicidal depressed patients. Suicides showed a significant lower HS than non-suicidal patients or depressive patients with suicidal ideation. No significant difference between suicide and suicide attempters groups. |
Case-control (5) |
Legend:
1The “Newcastle-Ottawa Scale (NOS) for assessing the quality of case-control and cohort studies” was used to evaluate the case-control (scores 0-10) and cohort studies (scores 0-12)
2The sample comprises patients treated on the Depression Ward of the Centre for Psychiatry, Weissenau in southern Germany between 1985 and 2002. The studies of Keller et al. (1991), Wolfersdorf et al. (1996) and Wolfersdorf et al. (1999) were conducted in the same centre
EDA = Electrodermal Activity; EDOR = ElectroDermal Orienting Response; HS = Habituation Score; MDD = Major Depressive Disorder; NS.SCR = Nonspecific Skin Conductance Response; SCL = Skin Conductance Level; SCF = Skin Conductance Fluctuation; SCR = Skin Conductance Response