... The ISTDP model has undergone repeated empirical testing, including, to date, over 25 randomized controlled trials (Lilliengren, 2022;Lilliengren, Johansson, Lindqvist, Mechler, & Andersson, 2016), a series of effectiveness studies (see Abbass, 2015), a variety of cost-effectiveness analyses (e.g., Abbass, Bernier, Kisely, Town, & Johansson, 2015;Abbass, Kisley et al., 2015), and qualitative research (Town, Salvadori, Falkenström, Bradley, & Hardy, 2017). Notably, most of these studies have targeted complex and treatment resistant patient populations, including treatment-resistant depression (Abbass, 2006;Town, Abbass, Stride, & Bernier, 2017), personality disorders (Abbass, Sheldon, Gyra, & Kalpin, 2008;Hellerstein et al., 1998;Winston et al., 1994), bipolar disorder (Abbass, 2002b;Abbass, Town, Johansson, Lahti, & Kisely, 2019), psychotic disorders (Abbass, Bernier, et al., 2015), psychiatric inpatients (Abbass, Town, & Bernier, 2013), severe mental illness with substance addiction (Frederickson, DenDooven, Abbass, Solbakken, & Rousmaniere, 2018) and prevention of electroconvulsive therapy in refractory depressed patients (Abbass & Bains, 2009). Additionally, ISTDP has been tested in patients with a variety of somatic disorders, including medically unexplained symptoms, functional disorders, and chronic pain (see Town & Driessen, 2013;Abbass et al., 2020;Abbass et al., 2021), with positive outcomes resulting in significant reduction in medical costs (Abbass, Kisely, Rasic, Town, & Johansson, 2015). ...