496 v. AFFECTI vE PROCESSES
ology of depression. Low approach motiva -
tion may be especially related to of the trans -
diagnostic clinical feature of anhedonia (see 
Treadway, Bossaller, Shelton, & Zald, 2012, 
for discussion).
At the neural level of analysis, MDD has 
been consistently linked to blunted reactivity 
to reward in striatal regions that are thought 
to subserve the approach system (see Whit -
ton, Treadway, & Pizzagalli, 2015, for re -
view). Of note, striatal hypoactivation in 
response to rewards has been observed not 
only in those diagnosed with MDD, but also 
in children of depressed parents (e.g., Gotlib 
et al., 2010) and at-risk adolescents (Olino et 
al., 2014), and has also been found to predict 
increases in depressive symptoms over a two-
year timespan in adolescence (J. K. Morgan, 
Olino, McMakin, Ryan, & Forbes, 2013), 
suggesting that this blunting of the approach 
system is not simply a second-  order conse -
quence of depressive experiences. Parallel 
electroencephalographic (EEG) evidence 
has emerged from studies showing that de -
pressed individuals and those with a history 
of depression exhibit lower activation in left 
anterior cortical areas than nondepressed 
persons; the same cortical regions have also 
been implicated in approach system sensitiv -
ity, as described earlier (see Harmon-  Jones, 
Price, Peterson, Gable, & Harmon-  Jones, 
2013, for review).
At the behavioral level, depressed indi -
viduals demonstrate lower responsiveness to 
rewards and less willingness to work for re -
wards than other people. For example, Piz -
zagalli, Jahn, and O’Shea (2005) found that 
individuals with elevated depressive symp -
toms failed to show the expected response 
bias toward one of two stimuli that was more 
frequently paired with a reward, and this 
deficit in reward learning predicted more 
anhedonic symptoms 1 month later. Individ -
uals with MDD, including those experienc -
ing first-  episode depression and individuals 
with high trait anhedonia, are less willing to 
engage in effort to obtain rewards and are 
more likely to disengage from demanding re -
ward tasks than are nondepressed individu -
als (Brinkmann & Gendolla, 2008; Tread -
way et al., 2012; Yang et al., 2016).
At the self-  report level of analysis, low 
BAS scores have been linked to depression 
cross-  sectionally and shown to predict a more severe course of depression over time 
(e.g., Campbell-  Sills et al., 2004; Kasch et 
al., 2002). Consistent with these findings, 
persons with depression also report less 
positive emotional responsiveness to antici -
patory reward cues (McFarland & Klein, 
2009) and are less likely to set and plan for 
specific approach-  oriented goals (Dickson 
& MacLeod, 2004). Overall, these findings 
provide strong support for the notion that 
underactive approach motivation, measured 
across multiple levels of analysis, is a central 
facet of vulnerability to depression and an -
hedonia.
Overactive Approach Motivation 
and Externalizing  Syndromes
There are a number of pathways though 
which high BAS sensitivity might be a risk 
factor for psychopathology. For example, in -
dividuals who have overactive approach sys -
tems might be predisposed to unrestrained 
and overenthusiastic pursuit of rewards that 
are intrinsically problematic, such as ille -
gal drug use resulting in substance use dis -
orders; that cause individuals to behave in 
ways that are regarded as abrasive or intru -
sive by others, as in the case of unabashedly 
seeking social dominance (e.g., as is com -
monly observed in psychopathy); under con -
ditions that are suboptimal for goal attain -
ment; or that interfere with completion of 
less rewarding tasks that are important for 
long-term adaptation. In particular, multiple 
theorists have suggested that high levels of 
BAS sensitivity are central to understanding 
the spectrum of externalizing disorders (see 
Fowles, 2001; Newman & Wallace, 1993).
There is considerable evidence supporting 
the notion that high BAS sensitivity is im -
plicated in a range of externalizing behav -
iors and syndromes. For example, Hundt, 
Kimbrel, Mitchell, and Nelson-  Gray (2008) 
found that high BAS self-  report scores were 
cross-  sectionally associated with symptoms 
of drug and alcohol abuse, psychopathy, and 
hyperactive–  impulsive attention-  deficit/hy -
peractivity disorder (ADHD) symptoms in 
an undergraduate sample. These findings 
converge conceptually with Honomichl and 
Donnellan’s (2012) prospective finding that 
surgency, a dimension of temperament that 
taps into appetitive motivations and bears a 