4. Discussion

This study was conducted on 50 ADHD children, their ages ranged from 6 to 15 years with a mean value of 9 ± 2.2 years, 86% of ADHD children were males and 14% were females, with a male/female ratio of 6.1:1, it is commonly reported in literature to have higher incidence in males than females. Similar to our results ElBaz et al. [Reference ElBaz, Kamal, Zahra, Khfagy and Youssef16] & Martin et al. [Reference Martin, Walters, Demontis, Mattheisen, Lee and Robinson17] revealed that male gender was predominant, at a male-female ratio of 7:1 and Mueller et al. [Reference Mueller, Fuermaier and Koerts18] found that ADHD is more common in boys as compared to girls.

In the present study, the inattentive type was 6% of cases while hyperactive type was 28% and mixed type was 66%, this was in agreement with the study done by Hergüner and Hergüner [Reference Hergüner and Hergüner19] who reported that the frequency of ADHD inattentive, hyperactive and combined type was 36.1%, 3%. was 60.9% respectively.

Twenty percent of the studied ADHD patients had positive history of consanguineous parents, by comparing the 3 subtypes studied ADHD patients: there was no statistically significant differences between them as regards the previously mentioned factor (p > 0.05). In agreement with our results, Elbaz et al. [Reference ElBaz, Kamal, Zahra, Khfagy and Youssef16] stated that there was no statistically significant difference between patients as regards consanguinity, three of the patients were the result of consanguineous marriage and 17 were not. In contrast to our result, Khoushabi et al. [Reference Khoushabi, Setareh-Forouzan, Moradi and Mohammadkhani20] found that positive consanguinity was significantly higher in the ADHD cases and Bener [Reference Bener21] also reported that there were statistically significant differences between ADHD and healthy children control subjects as regards consanguineous marriage of parents (p = 0.019). Moreover, Hasan et al. [Reference Hasan, Islam, Mahib and Arju22] revealed that consanguinity increases the risk of having ADHD in the next generation.

The current study showed that 26% of the studied ADHD patients had positive family history of similar disease without statistical significance among the different types of ADHD cases; (p > 0.05).Similar to our results, Elbaz et al. [Reference ElBaz, Kamal, Zahra, Khfagy and Youssef16] found that there was no statistically significant difference between cases and control as regards the family history of similar disease as 35% only had positive family history while 65% had negative family history.

There was statistically significant difference between ADHD subtypes as regards their mode of delivery 56.2% of mixed type cases were delivered by C.S. (p < 0.05). In agreement with our results, Amiri et al. [Reference Amiri, Malek, Sadegfard and Abdi23] suggested that participants born via C-section reported a significantly higher degree of internal restlessness than those born vaginally, which is considered an indicator of ADHD. In contrast to the present study Curran et al. [Reference Curran, Cryan, Kenny, Dinan, Kearney and Khashan24] found that no association was found between mode of delivery and ADHD.

There was no statistically significant difference between the 3 subtypes as regards their type of feeding, 78.8% of mixed type were breast fed while 21.2% were formula fed and 92.9% of hyperactive type were breast fed and 7.1% were artificially fed while all inattentive type were breast fed. Against our results, Adesman et al. [Reference Adesman, Soled and Rosen25] reported that compared with breastfed infants, ADHD was more common among formula-fed infants. Mimouni-Bloch et al. [Reference Mimouni-Bloch, Kachevanskaya, Mimouni, Shuper, Raveh and Linder26] found that children with ADHD were less likely to be breastfeed at 3 months and 6 months of age than children in the control group. They speculated that breastfeeding may act as a protective factor against developing ADHD later in childhood.

On comparing between the three types of ADHD cases as regards their anthropometric measures, there was statistically significant difference as regards their weight (p < 0.05) as combined type was more obese than other types, while there was no statistically significant difference between them in other parameters as height and body mass index (p > 0.05).

Elkins et al. [Reference Elkins, Saunders, Malone, Keyes, McGue and Iacono27] in his study provided meta-analytic evidence for a significant association between ADHD and obesity/overweight. Cortese et al. [Reference Cortese, Moreira-Maia, St. Fleur, Morcillo-Peñalver, Rohde and Faraone12] found that a significant association between obesity and ADHD was found for both children and adults. The pooled prevalence of obesity was increased by about 70% in adults with ADHD compared with those without ADHD and by about 40% in children with ADHD compared with those without ADHD.

There was no statistically significant difference between 3 subtypes of ADHD as regards their maternal illness during pregnancy, NICU admission; (p > 0.05). Amor et al. [Reference Amor, Grizenko, Schwartz, Lageix, Baron and Ter-Stepanian28] suggested that medical conditions that were more frequent in ADHD included several events occurring during the first 2 months of life: neonatal admission to hospital, having been in an incubator, oxygen therapy, general anesthesia and surgery being the most frequent. Arpino et al. [Reference Arpino, Marzio, D’Argenzio, Longo and Curatolo29] found that an increased risk of this disorder among children born to women experiencing a viral rash during pregnancy in their case-control study conducted to evaluate risk factors for ADHD.

In current study, levels of zinc and ferritin were measured and the deficient patients were supplemented by zinc (55 mg /day) and iron (6 mg/kg/day) for 6 months with assessment of degree of improvement according to their parents Conner’s Rating Scores and their Wecsler IQ test before and after treatment.

There was no statistically significant difference in the Wecsler IQ test before and after zinc supplementation. Similar findings were reported by many authors as Pongcharoen et al. [Reference Pongcharoen, DiGirolamo, Ramakrishnan, Winichagoon, Flores and Martorell30] showed that Supplementation with iron or zinc or both during infancy does not lead to long-term cognitive improvement in 9-y-old children. Rico et al. [Reference Rico, Kordas, López, Rosado, Vargas and Ronquillo31] also showed that daily supplementation with iron and/or zinc may be of limited usefulness for improving cognition in lead-exposed schoolchildren and there were no consistent or lasting differences in cognitive performance among treatment groups.On the other hand, De Moura et al. [Reference De Moura, de Moura, Alves, de Lima Vale, Dantas and de Araújo Silva32] found that zinc supplementation significantly increased the VIQ and PIQ scales which indicated that the schoolchildren increased their abilities in long-term memory, and recall, as well as alertness to detail, visual discrimination, planning, logical thinking, social knowledge, spatial analysis, abstract visual problem solving, visual analysis, and construction of objects. Moreover, zinc was more efficient in improving PIQ scores than in improving VIQ scores.

In the zinc deficient group in our study (group1), there was statistically significant improvement in oppositional disorder after zinc supplementation (P < 0.05) as regard mild cases became 5 cases instead of 3 before zinc supplementation and moderate cases become 10 instead of 6 and severe cases decreased to 11 instead of 17. In agreement with our result, Üçkardeş et al. [Reference Üçkardeş, Özmert, Ünal and Yurdakök33] found that there was clinically significant improvement in the oppositional behavior in the study group (p < 0.05) after supplementation with zinc in dose 15 mg/day for 10 weeks.In contrast, Kordas et al. [Reference Kordas, Stoltzfus, López, Rico and Rosado34] found that the regimen of supplementation did not result in consistent improvements in ratings of oppositional behavior in lead-exposed children for 6 months with zinc oxide at a dose 30 mg. Their study group was exposed to lead. The toxic substance exposed may also affect the response to zinc supplementation.

We also found that there was statistically significant difference in cognitive problems after zinc supplementation (P < 0.05) as regard mild cases become 8 cases instead of 5 before zinc supplementation and moderate cases become 13 instead of 12 and severe cases decreased to 5 instead of 9. Kordas et al. [Reference Kordas, Stoltzfus, López, Rico and Rosado34] in his double-blind, randomized trial in mixco, 602 first-grade children received 30 mg zinc oxide daily for 6 months, found that at follow-up, parent ratings of cognitive problems decreased.

On comparing between group 1 cases with zinc deficiency in our study as regards inattention subscale, there was highly statistically significant difference after zinc supplementation (P>0.001) as regards mild cases became 10 cases instead of 9 before zinc supplementation and moderate cases became 6 instead of 5 and severe cases decreased to 10 instead of 12. Üçkardeş et al [Reference Üçkardeş, Özmert, Ünal and Yurdakök33] study supported these findings, it was done in a low-income district primary school in Turkey, children in each class were randomized either to the study group to receive 15 mg/day elemental zinc syrup or to placebo group to receive the syrup without zinc for 10 weeks. They found that the mean Conner's Rating Scale for Parents scores on attention decreased significantly in the study group after supplementation. Also, Kordas et al. [Reference Kordas, Stoltzfus, López, Rico and Rosado34] found that at follow-up, parent ratings of inattention decreased. In contrast to our findings, Bilici et al. [Reference Bilici, Yıldırım, Kandil, Bekaroğlu, Yıldırmış and Değer35] suggested that zinc sulfate was statistically superior to placebo in reducing both hyperactive, impulsive and impaired socialization symptoms, but not in reducing attention deficiency symptoms.

In our present study, there was statistically significant improvement in hyperactivity after zinc supplementation (P>0.05) as regard moderate cases became 6 cases instead of 3 before zinc supplementation and severe cases decreased to 19 instead of 22.In agreement with our results, Biliciet al. [Reference Bilici, Yıldırım, Kandil, Bekaroğlu, Yıldırmış and Değer35] in his large randomized clinical trial, 400 children with a primary DSM-IV diagnosis of ADHD (328 boys and 72 girls, mean age 9.6 years) were randomly assigned to a 12-week double-blind treatment with zinc sulfate (150 mg/day, n = 202) or placebo (n = 198). The children treated with zinc sulfate showed marked improvements in hyperactivity and impulsivity but not inattention, as assessed with the ADHD Scale, Conners’ Teacher Questionnaire, and DuPaul Parent Ratings of ADHD.

On the other hand, Kordas et al. [Reference Kordas, Stoltzfus, López, Rico and Rosado34] reported that zinc seemed to be related to behavior problems and among children with zinc deficiency; those who were supplemented with zinc, the mean oppositional behaviour ratings by parents declined significantly but not hyperactivity.

Also there was statistically significant improvement in emotional liability after zinc supplementation (P < 0.05) as regard moderate cases become 7 cases instead of 3 before zinc supplementation and severe cases decreased to 18 instead of 23. Brown et al. [Reference Brown, Wuehler and Peerson36] reported that a number of zinc-related behavioral abnormalities have also been included as changes in mood, loss of affect and emotional liability, anorexia, dysfunction of smell and taste, irritability, and depression.

We also found that there was statistically significant improvement in impulsivity subscale after zinc supplementation (P < 0.05) as regards moderate cases became 1 case instead of 9 before zinc supplementation and severe cases decreased to 16 instead of 21. Similarly, Bilici et al. [Reference Bilici, Yıldırım, Kandil, Bekaroğlu, Yıldırmış and Değer35] stated that the children treated with zinc sulfate at dose 150 mg/day for 12 weeks showed marked improvements in hyperactivity and impulsivity. Akhondzadeh et al. [Reference Akhondzadeh, Mohammadi and Khademi37] also found that zinc either alone or in combination with drug treatment, also seems to improve parent and teacher ratings of ADHD, hyperactivity, or impulsivity.

In our study, in group2 (zinc and ferritin deficient), there was statistically significant improvement in the verbal and total I.Q test before and after zinc (55 mg/day) and iron (6 mg/kg/day) supplementation for 6 months (P < 0.05), but there was no statistically significant improvement in performance IQ (P > 0.05).

In line with our results, a randomized controlled trial of iron and zinc supplementation in infants was conducted by Pongcharoen et al. [Reference Bener21] in Thailand, 675 infants aged 4–6 months were recruited, of whom 609 completed the study. Infants were randomly assigned to 4 groups: 10 mg Fe in the form of ferrous sulfate, 10 mg Zn in the form of zinc sulfate, 10 mg Fe plus 10 mg Zn, or a placebo. Infants received supplements on a daily basis for 6 months, Cognitive performance was assessed by using the Wechsler Intelligence Scale for Children–third edition and found that no significant differences in performance IQ scores were observed between groups, there was also no significant differences in verbal and total IQ scores, also Hermosoet al. [Reference Hermoso, Vucic, Vollhardt, Arsic, Roman-Viñas and Iglesia-Altaba38] found that there was no statistically significant improvement in IQ in an Indonesian study in children who received 2 mg/kg/day iron for 3 months compared to the control group.

In group 2, there was statistically significant improvement in all Conner’s rating scale including oppositional, cognitive problems, hyperactivity, impulsivity, emotion liability and inattention subscales after iron and zinc supplementation for 6 months (P < 0.05). In Consistent with our findings, Kordas et al. [Reference Kordas, Stoltzfus, López, Rico and Rosado34] reported that there was also an iron by zinc interaction. Children with Zn deficiency receiving either placebo or the combined treatment had greater declines in mean hyperactive score than the other 2 groups (iron alone and zinc alone). In terms of teacher ratings, children who received iron had a significantly greater decline in mean oppositional scores than children who did not receive iron. On the other hand, children with depleted iron stores at baseline who received iron supplements had greater increase in mean cognitive problem ratings than children who did not get iron.

In Group 3 (zinc and ferritin non deficient) who were on Atomoxetine only, there was no statistically significant difference in their verbal, performance and total I.Q test (p > 0.05). In contrast to our study, Yang et al. [Reference Yang, Gao, Li and Zhao39] reported that after 6 months of Atomoxetine treatment, children with ADHD showed significant improvement in FIQ (p = 0.002) and PIQ (p = 0.011), and in agreement with our results there is a non-significant improvement trend in VIQ.

Also, in group 3 there was statistically significant improvement in their cognitive problems, hyperactivity and impulsivity (P < 0.05). Weiss et al. [Reference Weiss, Tannock, Kratochvil, Dunn, Velez-Borras and Thomason40], found that Conner’s rating total scores were significantly lower for children treated with Atomoxetine compared with those treated with placebo (p =.001). Similar results were observed for the inattentive (p =.016) and hyperactive/impulsive subscales (p <.001). Also Kilincaslan et al. [Reference Kilincaslan, Mutluer, Pasabeyoglu, Tutkunkardas and Mukaddes41] in his study out of 37 participants, 32 completed the 12-week period on ATX. On the ADHD- parent Rating Scale, there were significant reductions between baseline and 4th week, and between baseline and 12th week in total, hyperactivity, and inattention scores. Besides, the difference between baseline and 12th week was also significant in impulsivity. Twenty-one (56.8%) of the patients showed improvement in ADHD total score. The percentage of patients showing improvement in inattention, hyperactivity, and impulsivity scores was 48.6%, 45.9%, and 45.9%, respectively. Moreover, Fujioka et al. [Reference Fujioka, Takiguchi, Yatsuga, Hiratani, Hong and Shin42] reported a significant improvement in ADHD scores during the follow-up period with methylphenidate or Atomoxetine medication for inattentive symptom score, hyperactivity/impulsivity symptom.

There is some evidence that using zinc in combination with stimulant medications will help to improve ADHD symptoms and possibly lead to lower dose requirements, with as much as a 37% reduction in the dose of medication [Reference Bloch and Mulqueen9].

In our present study we found that dose of Atomoxetine had been decreased in 30 ADHD children after zinc and iron supplementation. While in zinc only deficient group, 21 children (52.5%), Atomoxetine dose had been decreased after zinc supplementation.

Supporting our results, Akhondzadeh et al. [Reference Akhondzadeh, Mohammadi and Khademi37] in his 6-week randomized, double-blind, placebo-controlled trial, the effects of zinc sulfate (55 mg/day) plus methylphenidate (1 mg/kg/day) were assessed in 44 children with ADHD (26 boys and 18 girls, mean age 7.9 years). Add-on treatment with zinc sulfate resulted in a greater improvement in ADHD symptoms (Teacher and Parent ADHD Rating Scale) than the sole administration of methylphenidate.