798 vIII. EMERGING  ISSuES AND  NEW  DIRECTIONS
The existing literature points to changes 
mainly in neuroticism due to pharmacologi -
cal intervention, most likely a result of the 
effectiveness of drugs to treat depression and 
anxiety, which are facets of neuroticism. Yet 
there is a rich oral history on the effect of 
lysergic acid diethylamide (LSD), mescaline, 
and psilocybin (magic mushrooms), affect -
ing one in a deep spiritual and transcendent 
level, potentially altering the personality 
(Unger, 1963). Most of the reported changes 
were retrospective, and without any system -
atic assessment of personality, mirroring the 
take-it-with-a-grain-of-salt statements some 
may make after seeing a “life-  altering” con -
cert or when someone finds religion. An ex -
ception is a nearly 60-year-old study on the 
effects of a large single dose of LSD. Chang -
es in Minnesota Multiphasic Personality In -
ventory (MMPI)-assessed personality were 
found after 2 months for most participants. 
However, these changes tended to not per -
sist, as only some participants evidenced 
change at a 6-month follow-  up. A more re -
cent, small sample study also found evidence 
of short-term change in a group that took 
LSD displayed increased openness over 2 
weeks compared to a control group (Lebedev 
et al., 2016). Some evidence suggest changes 
are not just short term. A study in which 
participants took a high dose of psilocybin 
found increases in openness after a 1-year 
follow-  up, with no changes for the any of 
the remaining Big Five traits. These changes 
were mainly driven by those who had greater 
mystical experiences during their mushroom 
trip (MacLean, Johnson, & Griffiths, 2011). 
Another study found changes in all Big 
Five traits except for agreeableness after 3 
months (Erritzoe et al., 2018). The potential 
for meaningful change and shifting attitudes 
about psychedelics have prompted more re -
searchers to study the effects of psychedelics 
on changing thoughts, feelings, and behav -
iors (Pollan, 2019).
Strengthening  Self‑Control
Low levels of self-  control are blamed for a 
number of societal ills, from eating an extra 
piece of cake to missing important work 
meetings (Baumeister & Tierney, 2011). The 
ego control model of self-  control states the self- control can be conceived as a muscle, 
and much like a muscle, self-  control can be 
strengthened through sustained practice. 
Numerous researchers have attempted to 
intervene and train self-  control (e.g., Gail -
liot et al. 2007; Muraven, 2010; Oaten & 
Cheng, 2007). In each of these studies, par -
ticipants are asked to do various activities 
that typically deplete self-  control, such as 
regulating speech or diet, using one’s non -
dominant hand, or practicing with a hand -
grip for periods ranging from 2 weeks to 4 
months. Gains in self-  control were found 
in a recent meta-  analysis of self-  control 
training interventions in which people were 
randomly assigned to practice at activities 
thought to deplete self-  control (Friese, Fran -
kenbach, Job, & Loschelder, 2017). How -
ever, there are concerns of small-study bias 
driving these results, calling into question 
the efficacy of these types of interventions. 
Furthermore, a replication study using tra -
ditional ego depletion, as well as standard 
questionnaires as measures of self-  control 
that used a larger sample size and complet -
ed training and follow-  up assessments over 
a longer period of time, found no evidence 
for the effectiveness of these interventions 
(Jackson, Kube, & Mike, 2020; Lee & 
Kemmelmeier, 2017).
Health  Interventions
One difficulty in parsing the health interven -
tion literature (e.g., Glanz & Bishop, 2010) 
is that many health interventions focus on 
changing health behaviors (e.g., exercise, 
diet) that conceptually overlap with as -
sessment of personality traits such as ex -
traversion and conscientiousness (Jackson, 
Weston, & Schultz, 2017). Outside of the 
measurement overlap issues, the few inter -
ventions that assess personality pre- and 
postintervention find limited change. For 
example, a meta-  analysis of interventions 
to improve the health of those with coro -
nary heart disease (behavior modification 
and health education) found no subsequent 
changes in anxiety or depression, the only 
personality variables assessed (Dusseldorp, 
van Elderen, Maes, Meulman, & Kraaij, 
1999). In contrast, a 2-month hostility inter -
vention led to changes in both hostility and 