# Effects of Physical Exercise on Substance Use Disorder: A Comprehensive Review
## 3 Results
### Assessment and Impact of Physical Exercise on the Quality of Life of Individuals with SUD
#### 3.1.1 Assessment and Effects of Physical Exercise on Depression  
Mental health issues, particularly depression, are among the most common comorbidities in individuals with SUD. The assessment of this construct is conducted using various scales, such as the Self-Rating Depression Scale (SDS) [46], the Beck Depression Inventory (BDI) [47], the Hamilton Rating Scale for Depression (HRSD) [48], and the depression factor within the Profile of Mood States subscale (POMS) [49]. The most frequently used tool in the reviewed literature is the SDS, particularly for substance-dependent individuals, including those addicted to methamphetamine (33.33% of studies using this questionnaire), amphetamines (33.33%), and alcohol (33.33%). The SDS consists of 20 items, with half scored inversely and the other half directly, so that higher scores indicate more severe depression. The literature examining the effects of physical exercise on depression is extensive. Previous meta-analyses provide robust evidence supporting the efficacy of physical exercise in reducing symptoms of depression among individuals with SUD, as measured through standardized mean differences (SMD) (SMD = \(-0.47\); z = \(2.76\); \(p<0.01/\text{SMD}=-0.40\); \(Z=6.24\); \(p<0.01\)) [11; 45]. Depression and Types of Physical Exercise in Intervention Programs  
An analysis of studies that measure depression as a relevant variable in individuals with SUD shows that most studies implement three types of interventions: mind-body exercise (Tai Chi or Yoga) [26; 50; 51], aerobic exercise (typically at moderate intensity) [43; 52; 53], or moderate aerobic exercise combined with strength training [18; 19; 54; 55]. Most of the studies that proposed intervention programs using mind-body disciplines did not report significant improvements in depression levels [50; 56; 57]. However, all the studies indicate that this type of exercise has a greater effect on reducing depression than traditional treatments (psychological therapy and/or pharmacological therapy). A recent systematic review and meta-analysis [45] reported that this type of physical exercise had a greater effect on reducing depression than standard therapy, reinforcing earlier findings. This type of exercise demonstrated a small but significant overall effect (SMD = \(-0.33\); \(Z=2.67\); \(p<0.01\)), as measured using [PERSON]'s scale. A more recent meta-analysis showed greater reductions in depression levels in interventions that employed Tai Chi (SMD = \(-0.67\); \(Z=-2.47\); \(p=0.01\)) [22]. This suggests that, when implementing interventions involving this type of physical exercise, Tai Chi may be the preferred discipline. Regarding studies incorporating interventions aimed at improving cardiovascular and respiratory fitness through aerobic exercise (at 60% to 80% of maximum heart rate (HRmax)) in individuals with SUD affected by depression, significant improvements in depressive states were observed compared to those receiving traditional therapy [43; 52; 53; 55]. Similarly, the most recent meta-analysis reported a large effect size for this type of intervention on depression improvement (SMD = \(-0.85\); \(Z=-2.51\); \(p=0.01\)) [22]. Finally, aerobic exercise combined with strength training (15 min per session of resistance exercises targeting large muscle groups) also reported improvements similar to [18; 19] or greater than [55] interventions that included continuous aerobic exercise (25 min per session). Duration, Frequency, and Intensity of Physical Exercise for Reducing Depression in Individuals with SUD  
There is significant heterogeneity in the frequency and duration of the interventions analyzed, demonstrating a lack of consensus in the literature regarding the optimal dose of physical exercise required to maximize improvements. In the studies reviewed [26; 35; 43; 45; 54; 55; 56; 58; 59; 60], no clear direct relationship has been found between the frequency and duration of training programs and their effect on depression.