To the best of our knowledge, this study represents the first attempt to apply the hctsa method for classifying resting-state EEG data into healthy and MDI groups. The objective is to evaluate the efficacy of hctsa and fundamental ML classification approaches in distinguishing between healthy individuals and those with MA dependence. Three distinct ML methods were assessed, specifically SVM, random forests RF, and LR. The results demonstrate that multiple feature combinations achieved 100% accuracy across all three methods.
Overfitting is a common challenge in ML, occurring when a model becomes overly adapted to the peculiarities of the training dataset, thus failing to recognize a generalized predictive pattern (Dietterich, 1995). To address overfitting, this study employed stratified k-fold cross-validation for accuracy assessment, ensuring that the testing dataset remained independent from the training dataset.
Numerous studies have focused primarily on individuals with addiction and implemented knowledge-based systems using EEG signals to aid human decision-making in forecasting substance dependence and generating insights for developing treatment strategies targeting substance abuse. Table 2 presents recent studies that aimed to identify MA abuse by incorporating EEG methodology into their research framework.
Table 2
Comparing the result of using different methods of classifying between healthy and MA addicted individuals. EPNN, Enhanced Probabilistic Neural Network; SVM, Support Vector Machine; RF, Random Forest; LR, Logistic Regression; DT, Decision Tree; MLP, Multilayer Perceptron; RBFN, Radial Basis Function Networks; AB, Ada Boost; GB, Gradian Boost
Authors | feature extraction method | Classification method | Accuracy | reference |
Ahmadlou et al. (2013) | visibility graph similarity in the gamma band | EPNN | 83% | (Ahmadlou et al., 2013) |
Shahmohammadi et al. (2016) | area of positive sections below the time window | subconscious craving-based algorithm | 80% | (Shahmohammadi, 2016) |
Khajehpour et al. (2019) | clustering coefficient, Node strength, Pairwise Weighted phase lag index | SVM | 93% | (Khajehpour, 2019) |
Ding et al. (2020) | power spectrum | RF | 89% | (Ding et al., 2020) |
SVM | 90% |
LR | 90% |
Chen et al. (2022) | spectral densities before and after virtual reality | SVM | 36% | (Li et al., 2022) |
LR | 64% |
DT | 84% |
RF | 68% |
MLP | 72% |
RBFN | 72% |
AB | 68% |
GB | 76% |
Ahmadlou et al. pioneered the application of resting-state electroencephalography (rEEG) in distinguishing MA abusers from non-drug-using controls. Their research involved assessing individuals with a history of MA abuse, revealing significant disruptions in functional connectivity within the gamma band. These findings provided valuable insights into the neurophysiological consequences of MA abuse (Ahmadlou, 2013). Shahmohammadi et al. conducted a study employing event-related potentials (ERP) to differentiate between MA abusers and control subjects. The researchers utilized the area under the curve (AUC) of windowed ERPs, elicited by a visual paradigm comprised of both drug-related and neutral imagery. This novel approach proved to be effective, as it facilitated the differentiation between MDI and NC with an accuracy rate of 80% (Shahmohammadi, 2016).
In a more recent study conducted by Ding et al., the authors developed RF, SVM, and LR models based on power spectrum density. These models demonstrated superior accuracy, achieving rates of 89%, 90%, and 90% respectively (Ding, 2020). A further developed SVM model, augmented by an array of features such as the clustering coefficient, node strength, and the Pairwise Weighted Phase Lag Index (WPLI), demonstrated a superior predictive accuracy, quantifiably reaching 93% (Khajehpour, 2019). Chen et al. employed virtual reality as a method of differentiation, utilizing eight distinct machine-learning techniques. Nevertheless, it was the DT algorithm that produced the most accurate results, boasting a commendable accuracy rate of 84% (Li, 2022).
ML methodologies are also employed in the medical field to differentiate between healthy individuals and other kinds of addiction such as alcoholism. Prior research utilizing SVM and LR classifiers has demonstrated a classification accuracy ranging from 85 to 95 percent (Bae et al., 2017; Mumtaz et al., 2018; Mumtaz et al., 2017). Farsi et al. achieved a substantial accuracy of 93 percent utilizing a Long Short-Term Memory (LSTM) computational model (Farsi et al., 2020). The highest accuracy in distinguishing between healthy individuals and those with alcoholism is attributed to two recent studies; Salankar et al. (Salankar et al., 2022) employed four distinct classification methodologies, utilizing three features derived from Second Order Difference Plots. Remarkably, they achieved an accuracy rate of up to 97% when implementing RF and SVM classifiers. However, the accuracy escalated to an impressive 99% when they utilized the Multilayer Perceptron (MLP) classifier. Li et al. (Li and Wu, 2022) employed advanced deep learning techniques, achieving varying levels of accuracy with four different models: Convolutional Neural Network (CNN), LSTM, Bidirectional Long Short-Term Memory (Bi-LSTM), and a combined CNN + Bi-LSTM model. The respective accuracies for these models were reported as 96%, 87%, 91%, and 97%. Moreover, the authors successfully refined their model, resulting in a significant increase in performance with an impressive accuracy rate of 99%.
The present study acknowledges several limitations that warrant consideration. Firstly, the recruitment of solely male substance users significantly restricts the generalizability of the research findings. Consequently, future research should be multi-centric and incorporate both genders to adequately address this limitation. The number of participants in our study is also limited which must be considered in future studies. So, Further investigation using different samples is necessary to evaluate the generalizability of these trained models.
The second limitation pertains to the study's inability to account for instances of polydrug consumption. It is plausible that individuals engaged in polydrug use may exhibit unique EEG patterns, differentiating them from those exclusively dependent on MA. Therefore, an inclusive approach that considers polydrug users is essential for a more comprehensive understanding of the relationship between EEG patterns and substance abuse in future studies. Additionally, subsequent studies should aim to conduct a comparative analysis of EEG patterns between MDI and those dependent on other substances, such as cocaine, to determine whether the identified EEG patterns are specific to MA use.
Thirdly, this study primarily aimed to explore the feasibility of utilizing ML methodologies to differentiate between individuals who consume MA and healthy individuals based on EEG data. To enhance the applicability of these findings as markers for detecting MA cravings, it is necessary to measure craving levels and other variables such as treatment adherence. Further research is therefore warranted. Additionally, it is possible that after a year-long period of sobriety and treatment, the MA-using group could potentially resemble the healthy control group. To obtain a more nuanced understanding of this possibility, future research should involve diverse sample groups, including untreated MA users, for instance.
In conclusion, this study represents a pioneering attempt to apply the hctsa method combined with ML classification approaches to distinguish between healthy individuals and those with MA dependence using resting-state EEG data. The results demonstrate promising efficacy, with multiple feature combinations achieving 100% accuracy across three ML methods. The study addressed the challenge of overfitting through stratified k-fold cross-validation, ensuring independent testing datasets. Previous studies in the field have also utilized EEG methodologies to identify MA abuse, providing valuable insights into the neurophysiological consequences of substance dependence. However, there are limitations to consider, including the need for multi-centric studies with gender diversity, the inclusion of polydrug users, and comparative analyses with other substance dependencies. Future research should explore the potential of EEG patterns as markers for MA cravings, considering variables like treatment adherence and craving levels, and involve diverse sample groups to further enhance understanding.