|"Maybe the 80s will be like radical or something"|
Omega-3 fatty acids, including α-Linolenic acid (ALA), Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) sourced from things like fish have been the stuff of controversy and debate over the years, particularly focused on their potential link with various facets of child development. I don't want to get into all the nitty-gritty of discussions but suffice to say that this is an area which, for quite a few years, seemed to be cast into the scientific desert. In more recent times, science has started to more systematically examine the possibility of a link between omega-3 fatty acids and development and how supplementation might be indicated for some (see here).
Specifically with ADHD in mind, omega-3 fatty acids boasts quite a thriving research base. The one go-to article that many people have relied on in recent years was the Cochrane Review of PUFAs (polyunsaturated fatty acids) by Gillies and colleagues  that concluded: "Overall, there is little evidence that PUFA supplementation provides any benefit for the symptoms of ADHD in children and adolescents". Bearing in mind that review looked at research up to August 2011, the evidence base has moved on somewhat since then, with various controlled trials publishing results as per those from Milte and colleagues  and Richardson and colleagues  specifically based on analysis of the omega-3 fatty acids. Although not wholly positive , the combined results seem to imply that for some with ADHD, there may be certain benefits  to be had following certain supplementation.
There's little more for me to say on this topic aside from pointing out the need for further investigation on the hows and whys of fatty acid deficiency/supplementation with at least some diagnosed with ADHD and how this might also translate into other conditions where ADHD may be quite frequently comorbid (see here). As part of a wider body of peer-reviewed research suggestive that dietary variables may play some role for some with ADHD (see here and see here) I'm minded to suggest that food and nutrition should rank further up the research priorities hierarchy when it comes to intervention and ADHD.
So then, Urge Overkill? (if you don't recognise the band name, you'll probably recognise the song).
 Hawkey E. & Nigg JT. Omega-3 fatty acid and ADHD: Blood level analysis and meta-analytic extension of supplementation trials. Clin Psychol Rev. 2014 Jun 2;34(6):496-505.
 Gillies D. et al. Polyunsaturated fatty acids (PUFA) for attention deficit hyperactivity disorder (ADHD) in children and adolescents. Cochrane Database Syst Rev. 2012 Jul 11;7:CD007986.
 Milte CM. et al. Eicosapentaenoic and docosahexaenoic acids, cognition, and behavior in children with attention-deficit/hyperactivity disorder: a randomized controlled trial. Nutrition. 2012 Jun;28(6):670-7.
 Richardson AJ. et al. Docosahexaenoic acid for reading, cognition and behavior in children aged 7-9 years: a randomized, controlled trial (the DOLAB Study). PLoS One. 2012;7(9):e43909.
 Dubnov-Raz G. The effect of alpha-linolenic acid supplementation on ADHD symptoms in children: a randomized controlled double-blind study. Front. Hum. Neurosci. 2014; 8:780.
 Widenhorn-Müller K. et al. Effect of supplementation with long-chain ω-3 polyunsaturated fatty acids on behavior and cognition in children with attention deficit/hyperactivity disorder (ADHD): a randomized placebo-controlled intervention trial. Prostaglandins Leukot Essent Fatty Acids. 2014 Jul-Aug;91(1-2):49-60.
Hawkey E, & Nigg JT (2014). Omega-3 fatty acid and ADHD: Blood level analysis and meta-analytic extension of supplementation trials. Clinical psychology review, 34 (6), 496-505 PMID: 25181335