Is there explanation of persistent laziness? As we say when we feel happy there are some biological explanation of some feelings like happiness and sadness as they explain here.

So I say whatever we feel can be explained in biological way, so what about when one feel lazy? In the way that he/she is having no motivation (not due to lack of energy). Is there any biological explanation of someone being lazy like no motivation to do anything and that remain for long time say months.



PS: this website describes the kind of laziness I am too talking about, and I quote from this website: 


  I am really tired [...] my entire life. Every morning when I wake up my first thought is “I wonder when I can take a nap”. Even while I’m thinking it I realize the futility in this thought; I haven’t actually taken a “nap” in
  months.
Low motivation can stem from a variety of different things. A lot of it boils down to low neurotransmitter activity in areas traditionally associated with motivation. The neurotransmitter 'dopamine' plays a significant role in the regulation of pleasure, reward, and motivation. The neurotransmitter 'serotonin' is thought to regulate emotional well-being and happiness. 'Norepinephrine' is considered to be responsible for vigilance in concentration, and the locus coeruleus (the principal site for norepinephrine synthesis) is said to receive input from the orbitofrontal cortex, which is an area of the brain also involved with reward, motivation, and impulse control.

With low neurotransmitter activity comes certain behaviors and mental states that are commonly associated with specific mental disorders. Low levels of serotonin (and, henceforth, dopamine and norepinephrine, insofar as they are mediated by serotonin) can result in clinical depression. Low levels of dopamine and norepinephrine are thought to be associated with disordered attention, executive functioning, and motivation disorders, such as attention deficit disorder and sluggish cognitive tempo (SCT).

Persistent laziness can also be a learned trait. Norepinephrine also seems to be closely involved with the anterior cingulate cortex (ACC), which plays a role in the control of certain autonomic functions such as heart rate. Norepinephrine also seems to be somewhat involved with urgency (fight-or-flight), and is thought to be activated in times of physiological stress. From a social standpoint, if there is no social pressure to work, then the activation of norepinephrine needn't happen. It is also worth noting that stimulation of the ACC is thought to provide relief for those suffering from major depression.

Long-term laziness implies that any some combination of the above has been occurring for a long period of time. The best way to counteract long-term laziness would be to find a happy medium between behavioral adjustment and (in more extreme cases) medical treatment.