# Spectral and Nonlinear Analysis of Electrodermal Activity in Adolescent Anorexia Nervous
## 6 Discussion  
To the best of our knowledge, this study was the first to describe features of the sympathetic cholinergic regulatory system using spectral and nonlinear characteristics of EDA in AN adolescents before starting a treatment. The results can be summarized as follows: (1) several indices of time (SCL) \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Anorexia Nervous (n = 25)** & **Controls (n = 25)** & \(p\) **Value** \\ \hline \multicolumn{4}{c}{**Time-domain indices of EDA**} \\ SCL (\(\mu\)S) & 0.67 (0.32–2.21) & 2.10 (0.97–3.23) & 0.041 \\ NS.SCRs & 0.50 (0.00–1.00) & 1.00 (0.00–2.00) & 0.257 \\ \hline \multicolumn{4}{c}{**Frequency-domain indices of EDA**} \\ EDA-VLF (\(\mu\)S\({}^{2}\)) & 18.85 (0.28–56.66) & 238.84 (41.39–798.81) & 0.001 \\ EDA-Symp (\(\mu\)S\({}^{2}\)) & 16.33 (3.09–103.79) & 815.60 (125.69–1427.03) & 0.0001 \\ EDA-HF2 (\(\mu\)S\({}^{2}\)) & 1.45 (0.37–5.94) & 1.73 (0.44–5.07) & 0.684 \\ EDA-VHF (\(\mu\)S\({}^{2}\)) & 1.45 (0.37–5.94) & 0.21 (0.03–1.07) & 0.765 \\ \hline \multicolumn{4}{c}{**Nonlinear indices of EDA**} \\ ApEn & 0.59 (0.41–0.82) & 0.67 (0.45–0.82) & 0.674 \\ SampEn & 0.48 (0.28–1.18) & 0.48 (0.27–0.81) & 0.562 \\ SIE & 2.14 (2.06–2.65) & 2.35 (1.51–2.76) & 0.734 \\ \(\alpha\)1 & 1.01 (0.65–1.20) & 0.94 (0.77–1.17) & 0.779 \\ \(\alpha\)2 & 0.49 (0.07–0.73) & 0.11 (0.05–0.31) & 0.032 \\ \hline \multicolumn{4}{c}{**Index of peripheral temperature**} \\ PT (\({}^{\circ}\)C) & 30.53 (25.93–33.46) & 31.43 (28.94–32.54) & 0.487 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Parameters of electrodermal activity and peripheral temperature. and frequency (EDA-VLF and EDA-Symp) analysis were significantly lower, indicating insufficient sympathetic cholinergic activity already in adolescent anorexia nervosa; (2) in contrast, the index of DFA-\(\alpha\)2 showed a different pattern compared to the time and spectral EDA characteristics--it was increased in anoretic patients thus providing independent and novel information related to altered complexity in sympathetic cholinergic regulatory network in anorexia; (3) correlation analysis revealed that BMI is positively associated with SCL and PT indicating possible alteration of sympathetically mediated and thermoregulatory mechanisms in AN, which could be induced by extensive reduction in body weight. Several mechanisms are proposed. First, reduced SCL is in accordance with other studies that revealed a lower mean of tonic EDA in AN adults [18; 20] and extend these findings into the adolescent age group. Additionally, our study revealed statistically important decrease of EDA in spectral-domain (EDA-VLF, EDA-LF and EDA-Symp) in AN compared to controls. Moreover, we found a positive correlation between SCL and EDA-VLF, and between SCL and EDA-Symp. Thus, we assume that EDA evaluation by SCL, EDA-VLF and EDA-Symp indices represents a sufficient non-invasive tool for assessment of sympathetic cholinergic underactivity linked to AN. Our previous study revealed reduced sympathetic activity based on blood pressure variability analysis in newly diagnosed AN girls, indicating nutritional trajectory as an adaptation process associated with bodyweight control from \"normal weight to underweight\" [8]. Thus, we assume that acute phase of adolescent AN is characterized by sympathetically mediated autonomic hypoactivation which could only partially be ascribed to the reduced body weight measured by BMI associated with reduced basal metabolism. Specifically, neurobiological features such as hormonal deficiencies (e.g., decreased level of leptin and increased level of ghrelin), neurotransmitters (e.g., serotonin and dopamine) [36; 37; 38] and electrolyte dysfunctions (e.g., mainly potassium) [39] could play an important role in AN-linked sympathetic underactivity. Notably, leptin as an important molecular signal of energy abundance is closely linked to sympathetic regulation [40; 41], and reduced leptin concentrations associated with sympathetic hypoactivity were found in anorexia nervosa [42].