The mind is its own place, and in itself can make a Heav'n of Hell, a Hell of Heaven (John Milton).
Today, any scientific blueprint for getting rid of suffering via biotechnology is likely to be reduced to one of two negative stereotypes.
The first centres on soma Aldous Huxley's spurious evocation of the ideal pleasure-drug. Soma is taken by the brainwashed and manipulated dupes of the ruling genetic caste in Brave New World. A cross between a tranquilliser and a non-addictive opiate, soma allows Huxley's utopians to enjoy imbecilic, drug-induced bliss to offset their empty consumerist lives, and set the basis for a philistine society to abolish the intellectual progress.
The second stereotype features an intracranially self-stimulating rat. The little creature's enraptured frenzy of lever-pressing is eventually followed by death from inanition, self-neglect and immunological collapse.
In the case of humans, our reward-pathways are more anatomically diffuse than the average rodent.
At least with present-day electrode-placement techniques of intracranial self-stimulation, humans doesn't lead to uncontrolled hedonistic excess and death. Only depressed or deeply malaise-ridden human subjects compulsively self-stimulate when wired. In fact, exotically enriched states of consciousness can be transformed into the everyday norm of mental health, and hedonic enrichment needn't lead to entail getting stuck in a wirehead rut.
This is because the dopaminergic drugs tend to enhance 'incentive-motivation', and so increase exploratory behaviour, will-power and the range of stimuli an organism finds rewarding.
On the other hand, empathogen drugs like Ecstasy - which releases a lot of extra serotonin and little amount of dopamine - may potentially induce extraordinary serenity, empathy and love for others.
Why can't social engineering, politico-economic reform or psychotherapy - as distinct from germ-line genetic rewrites - make us durably happy?
Evolution provides at least a partial explanation for the endemic human misery, which lies in selection-pressure and the state of the unreconstructed vertebrate genome. It is conceivable that natural selection has engineered the 'encephalisation of emotion', resulting in our revulsion at the prospect of turning ourselves into wirehead rats.
The slanderous and misunderstood selfish DNA(*) could make its throwaway survival-machines feel discontented a lot of the time: a restless discontent is typically good for promoting its 'inclusive fitness', even if it's bad news for us. Eventually an ideal world would arise, in which our emotional, intellectual and physical well-being will be genetically predestined, and where suffering will be physiologically inconceivable.
Nature simply doesn't care, and the longer human beings are evolving, the more they will turn into God.
(*) Reference for clarification : 'Sequences of selfish DNA - making up approximately 10% of human genomic DNA and usually found near the centromere, the site of repressed recombination - result in no functional products. Although they do not directly cause problems, they can indirectly cause changes in the genome, such as a mutation due to an insertion into a functional gene. These repeated sequences are thought to be functionally important for the host organisms and contribute to the long-term evolutionary potential of a population (...)'
Thibault B, Gonzalez J, Stacy L. Biology Department. University of California, Berkeley.